I'm a little confused.  Are you saying you need them to remain in their qwerty positions, but otherwise want the Colemak layout?

If so, I'm confused because the W is the same in both Colemak and Qwerty.

And also if so, the layout is quite optimized.  If you force a weak letter like F onto the home row, the optimal layout will be drastically different, because the T will need to find its way back to the home row.

It's likely your problem can be solved some other way, and I think that's what others will ask you.  Things like, why do you need F to stay there?  And they will anticipate an answer such that they can provide you solutions to your issue while still using Colemak.

I will be working briefly on what I believe is a good layout with the W F U Y and Z X C V staying in place, while retaining similar Qwerty-esque learnability and distance to Colemak.  If that is indeed what you're looking for, I hope it will be of use to you.  If not, it was all for naught.

What I came up with is this:

. W D R J    Y U H P Q
T S N F L    G A E I O '
Z X C V ;    B M , K /

Colemak is still better in terms of my own inhouse metrics (for the most part), and also better in terms of distance, digraphs, etc.  But this is pretty damn good IMO, especially considering it's similarity to Qwerty and having the W F U Y Z X C V held in place.

So you can't put anything on them at all?  That is quite strange.  What do you currently do?

It sounds like you may be better off learning something like Vim, that way you can type well but also have your commands ergonomic and accessible.  Is this not an option for you?

kameloc:  Where the digraphs were sacrificed, it was to improve trigraphs that matter just as much.  Sometimes it's worth it to have some finger digraphs.  I welcome you to offer a layout you feel is more optimized than the one I offered, for the task of keeping W F U Y Z X C V the same as Qwerty.  It doesn't matter anyways, though, because that's not what he wants.  He wants a layout that doesn't use those keys at all.  Making room for 4 keys is pretty rough, but it may be an interesting alternative to modeful editors like Vi.

Besides being "optimized", "qwerty-like", and having W F U Y unused, what other goals do you have for the layout?  Do you require ZXCV to stay the same, or any other letters?

I'm pretty sure Emacs has a vi-like mode and can let you rebind keys all kinds of ways, but I don't use Emacs so I don't know.  Honestly, I use arrow keys quite a bit too.  I use the Ins/Home/PgUp/Arrow keys blocks quite a bit, since I am from Windows.

Putting those keys off to the right will probably be horrible; it will probably be better to move rarely used keys over there, but then you will have to reshuffle around the other keys as well.  A good layout that keeps those keys free will not be Colemak, but I can stir one up if you want.  Because you're moving so much to pinkies, it may very well be worse than Qwerty, let alone Colemak, as far as the typing on it goes.  It may be worth it, depending on how much you use arrows, but keeping it similar to Colemak and/or Qwerty is going to make that even harder.  Why the W F U Y keys BTW?  Y U for left right and W F for Up/Down?  Why not something symmetrical like RTYU, or TYZ/?

Ok:
1) I've programmed backspace & delete to either work as usual (correct a typing mistake), or to cut logical entites of text depending on situation. It works great and have resulted in far fewer keystrokes. I also use tab for Emacs special (and highly effective) auto-complete. It is used a lot.
2) After logging all keystrokes, it turns out that the most used keys are right, left, space, down, up, tab, delete, backspace in that order. The most common letter 'e' is far behind any of them. Figures (0-9) are hardly used at all.
3) The thumbs are strong fingers perfect for modifier keys for instance. To waste both of them on a single 'space' is ridiculous. Therefore, I've (just like Arensito) moved up the home row.
4) Left and right hand are too close to each other on QWERTY. I therefore move the right hand one column to the right. It's more comfortable, takes stress off the right pinkie, and introduce one extra column between the left and right hand that both index fingers can use instead.
5) An optimized layout for coding would involve cursor and edit keys on home row. An optimized layout for writing text (emails etc) would probably look something like Colemak. I don't want to switch between two different layouts, so I'm looking for some kind of compromise: use Colemak at a higher home row with the right hand one column to the right, and just exchange some keys in favor of cursor and editing keys.
6) It turns out that the fastest way to edit text is to use one hand for cursor movement and the other for editing.

Taking these points into account have so far resulted in:

* q dl bs p g j * l up dn * * *
rt a r s t d * lf n e i o * *
z x c v b k h m * * *
* * sp ct * rg tb * * *
(space key is a modifier for both thumbs to reach)

where dl = del, bs = backspace, up = up, dn = down, rt = return, lf = left, sp = space, rg = right, tb = tab

It might look strange, but since it is statistic driven, it's remarkable comfortable and fast. Now the question is where to put w, f, u, y? I've no problem with moving zxcv - an optimal layout for life is far more important than some stupid shortcut convention that easily could be reprogrammed anyway.

I have thought about modal editing (as in having a key that switches two different layouts - one with letters and one with editing), but according to my statistics there are quite many situations where the two are mixed every other key press. I'd go insane if I had to press the switch key each time. But maybe I'd change my workflow so that the net effect became positive. Hmmm... Maybe, maybe.

Yes, Kinesis is great, but it looks like hell, and I travel a lot and need a setup that works on laptops as well.

This is similar to what I'm using, and oddly enough I don't feel any less sane than a year ago (but then again, you don't notice those things yourself do you? ... hmmmm ...  :D  ). I don't use mode switching but a modifier though, since as you say it changes back and forth a lot and I'm not a seasoned Vi user (yet) who can juggle mode awareness at a whim. I find that for my uses, pressing CapsLock and then my extended mappings seems very effortless and fast. I even use Caps+Space instead of Enter and Caps+O instead of Backspace quite exclusively rather than making the relatively small pinky stretches to the real keys!

The benefits of staying in the home position while having the ability to, say, go to the end of a line (Y), mouse scroll (P/T), Page Up/Down (J/H) or select the previous word (Shift-Ctrl-N - not at all as hard as it sounds since you can hit all the necessary modifiers with one flat left pinky press!) with just a key press plus modifiers feels very strong. It has made me use other hot keys much more since I feel so much less dependent on the mouse now. And it isn't just for one program such as Vi, but for nearly everything!

I believe in keeping symbols, letters and 'action keys' somewhat separate. I don't intersperse the letter block with symbols, even at the AltGr level. And I don't put dead keys under letter keys for instance, but use all the symbol keys instead. And I like to have the 'action keys' on one easily reached 'extend' modifier. Some won't mind intermingling such keys, but I do and I feel that this consistency makes for a more harmonic and intuitive layout. Keeping track of advanced mappings, dead keys and extended mappings is far more advanced than the standard layouts, and I don't want to make it any more tricky than it already is. I'm still working out the kinks in my muscle memory after I moved the extended Del mapping the last time, heh.

If coding a lot though, you can't beat the efficiency of more advanced features such as those offered by Vi(m).

I have had that worry, but oddly enough my left pinky doesn't feel tired from all the pressing it has to do in the course of my day!

One consideration might be that I may have strong fingers, having played the piano and suchlike. It'd be interesting to have more people try this out. I've heard of a few others using similar setups, including the PKL's creator Farkas Máté, but I haven't heard any experience reports.

Another thought I'm making me is that it isn't the keypresses but the awkward stretches that matter the most, along with key hammering if you have bad habits. The CapsLock is never hammered even when I'm stressed, and the stretch is a small and straight outward one that feels okay to me. Once you strart using the CapsLock for something useful, you're shocked that it wasn't put to good use before as it's a really handy key to reach; this, of course, is already duly observed by Shai when making Colemak!

The setup saves me a lot of far more awkward contortions: I take care to keep my wrists straight which I believe to be very beneficial. Thus, the stretch to hit the Enter key with my right pinky is no fun at all. Most of the other extended mappings don't relieve stretching as much as hands flying around, which might conceivably make some of your underarm musculature unhappy but I don't think it matters much; thus, these other mappings are for the most part time savers rather than ergonomic wonders. But the Enter key is in very frequent use, so as a rough estimate I'd say that the extra strain I put on my left pinky is more than compensated for by not having to stretch my right pinky down-and-out - literally speaking!