Just wonder, why do you move the UNEI keys to the arrow positions?  I have noticed others doing that as well.  It kind of looks funny having the letter keys in the arrow key positions!

Pereant qui ante nos nostra dixerunt! ;-)

My own reasons for the UNEI swap were:
• I wanted a nubbed key in the N position, and didn't want to manhandle my N key to scratch out one. The Down key had a nub.
• Once that was in place, I felt that it looked cooler to move the entire UNEI arrow cross.
• Keep in mind also that the UNEI keys become the arrow cross in the Extend mod!

I prefer the name "A-Wing". Vroooaaar!!! ;-) It isn't "my" mod; I think it was invented by Cevgar. Wonderful, creative, crazy Cevgar!

I think the distance to the Tab key is perfectly acceptable. The distance to Caps may be a problem for the Extend mod though; not quite sure what to do about that but it has been suggested to use the old A key as Extend key instead, and put a bracket on the old Caps! That looks a bit messy but it could work well in practice. Or one could rearrange further, put the brackets on the top row and backtick on the Caps key?

The distance to LShift is as you say, what we ISO peeps were used to already. It's okay, I promise. ANSI users tend to be a little put off at first but I think they get used to it pretty quickly.

Yes, the opinion was that a double-wide mod is probably a bridge too far, at least on an ANSI board. If you make that single-wide instead you can keep the RShift in use and put LShift on the Alt key instead?

Also, that mod changes the expected positions of the right-hand number row which I found very confusing when trying it out.

____________________________________________________________
| ` | 1 | 2 | 3 | 4 | 5 | 6 | = | 7 | 8 | 9 | 0 | - | Back |
| Tab | q | w | f | p | g | [ | j | l | u | y | ; | ' | \  |
| Ext  | A | R | S | T | d | ] | h | N | E | I | O | Enter |
|      z | x | c | v | b | • | / | k | m | , | . | RShift  |
| Ctr | Wn | LSh |       Space        | RAlt | W | M | Ctl |
------------------------------------------------------------

Something like this? The key marked '•' could be the LAlt key. Alt is often used alone, to initiate menus. Not sure if you want AltGr on RAlt, or just an Alt key? AltGr is another wonder of the ISO world that ANSI users in general didn't take to, with the embarrassing result that most US typists can't use accents.

Putting the slash key in the middle isn't ideal (mine is where the apostrophe is on the above figure, but then I have room for the apostrophe between O and Enter). But it's okay I think. It's what the A-Wing and other ANSI mods does, too.

It does look interesting, I must say! How well the thumb shift works in practice remains to be tested.

SteveP99's suggestion is also worth considering:

Maybe it'd work better with the Shift on AltGr and Space unmoved, as suggested. But then, both Shift keys are on the right hand – would that be okay?

Both look nice. I do agree with you on the /? key issue, that place in the middle dump is not the optimal place for it.

Maybe you'll still grow to like the Wide mod as I and many did. One of its benefits is easier access to the RAlt/AltGr key (and all other right-side keys)! So uh, sorry, but that'd be my tip. :-) But for an ANSI user the quarters are cramped and you have to make sacrifices no matter what – pick your poison.

Another suggestion would be to put Shift on LAlt and LAlt on RAlt (or just trust that the RAlt will do everything you need!

One question though: When you go through all this trouble to find an Angle mod, you do want the DH-mod too I hope? I find it very comfortable to have a naturally curled home position instead of the forced straight line thinking.

Some users have complained that their RAlt key was gone; apparently it was a program that used that key specifically for something. But that may not concern you.

Myself, I love the AltGr key. Love it to pieces. It means two more shift layers (and potentially, two more Extend layers). These let me write all sorts of accents/currency/symbols and lesser-used letters. This is a great boon when writing other languages such as Icelandic but I'm guessing you don't do that. But also to get for instance the —€•®™†‡©¢÷×←↑→↓ symbols and more. The ability to write bulleted text in Notepad is nice.

   
    Fig.: Colemak [edition DreymaR] with Curl(DbgHk), Angle and Wide(Slash) ergonomic mods (or in short, Colemak[eD]-CAW; see my sig topic).

Note all the yellow keys: These are dead keys. AltGr+5 produces all the Greek letters for scientific and other purposes; AltGr+4 a bunch of currency symbols and some of the accent keys are overloaded with symbols too. Αωεσομε, eh? ;-) (See my PKL sig topic for more examples of Colemak[eD] dead key mappings.)

Of the two, I would go with this one. Using the right Alt key for Shift is a great idea, and by having the home keys further to the right, it will make that key even easier to access with your right thumb. Since you already use your left thumb for space, it means you can have separate functions for each of your two thumbs, which I believe you'll find to be extremely effective.

The only minor downside I can think of is if you need to do frequent mouse shift-clicks. But that's not a major issue for most people.

I would also swap /? with \| though, the rarer backslash key should be in that awkward centre position I think.

My keyboard has a split spacebar, so I have configured one side of the spacebar to be Shift.  Having Shift via a thumb is brilliant. The Shift key positions on a standard keyboard (ISO or ANSI) are terrible in my opinion.

Yay! Welcome to the ISO world, then! :-)

Hope your caps markings will be acceptable or replaceable to something acceptable.

I don't feel that we've wasted our time, but spent time developing solutions for other people in the same situation. We love a good keyboard discussion! ;-)

I have a hipster layout, I have a hipster layout! *squee*

Slick!

Is there a key cap that'll fit the ISO LShift key, though?

Not sure. ISO LShift is the same width as LAlt/RAlt; that is, 1.5 keys I think? Tab is 1/4 key wider and I think the ANSI \| may have Tab width?

The number one thing to make touch typing comfortable is to get an ergonomic keyboard with straight columns, and preferably concave well to accommodate different finger lengths. Related, try to get one with thumb pads so you can use thumbs to hold shift and hit enter and backspace. This will save your pinkies from major harm while improving keyboard usage comfort and efficiency.