I have to admit, I'd have gone with an 84 key "75%" keyboard myself, if not for deciding to go completely custom. Instead, I added one more column to the right (2 columns right of return, shift, etc), and came up with an 88 key layout. The nice part is that the right shift and modifiers can all be the proper size, so you can populate this with standard TKL basic key cap sets, without ending a special right shift or special modifiers.
