Thanks! Wouldn't it be possible to replace the switch-housings of the HHKB with the ones in the HiPro and then be able to use the caps? Its probably quite complicated but would it be possible?
The HHKB has the slider housings built into the case
But I know of at least a couple of Hi-Pro HHKBs that have been put together. I bet it's possible. I think livingspeedbump had such a board for a little while.
Any information out there about how to do this mod?
Full disclosure: it'll work, but it's $$$$
You'll need a 104UG for the right sized Spacebar, and a 108UG for Shift/Fn split.
You CAN put the caps on a standard topre slider (I just did it on the HiPro I'm typing on right now to verify), but they might be more 'wobbly'. The HiPro sliders provide a guide for the caps to slide down on, hence the 4 gaps on each side. Escape is a different profile from the number row, so you'll have either a duplicate key, or a similar key on the number row.
Here's the keys that won't match up: Control (it'll be Caps Lock instead), Backspace (|\), |\ (something you choose), Esc, Alt (Windows).
So, while it would likely feel nice and be pretty unique, IMO there's too many gotchas.