Ha, when I first started using my thumb Shift key (left spacebar), I used to do that DOuble CApital thing quite a lot at first. I think it was because it speeded up my shifting so much that my other fingers were already too far ahead. I quickly got used to it though, don't really have that problem any more.

Why don't you make your Alt key be a sticky shift then? Then you could just do a quick tap it with the thumb and continue typing.

PLEASE!!! (knelt smiley)

I'd suggest instead mapping the Left Windows key to be LeftAlt. In other words, LeftAlt just moves one key to the left (i.e, to its location on a Mac keyboard). Also, on a lot of keyboards, the physical keys for Win and Alt are often the same size, so you might even be able to switch them.

I considered switching Alt with Shift at one point, but decided it was better to leave the standard shift keys unchanged, to avoid problems whilst still learning the new Shift method.

Presumably if you did this, you'd end up with something like this:

(...with the thumb shift obviously being sticky!)

Windows-Key is the least important of the modifiers, so I think it's much less important where you put it. My laptop also doesn't have a RWin key either, but it does have a "menu" key, so I use that as my Windows key. Although I rarely use the Windows key, but it's nice to know its there! The loss of the Menu key doesn't matter because one of my Extend mappings emulates Menu key. And, I pretty much never use that either.

The benefit of having Shift (or in my case, Extend) in the LeftAlt position easily outweighs any minor inconvenience caused by having a non-standard Windows key.