If you're going split space, can you split it again? Like, 1/2, 1/4, 1/8, 1/16 etc.? I think that would work really well, especially for the smaller letters and symbols.
And I can't remember if you've settled on GMK, SA, or both, but I'd prefer if you switch back.
EDIT: Sorry, I thought this was for the new GMKSA keyboard. Wrong topic, ignore my first point.