Well my MX Red and Brown switches arrived in the mail today - Thanks 7bit!
I now have to resist rushing to make both new boards, one Red, one Brown, so I can fully document the build for posterity...
Below you can see a picture of two OneHand keyboards in the TwoHand configuration, together with my old Matias Halfkeyboard for reference.
The MX Red and MX Brown switches are much quieter than the MX Blue in my original - which my wife will appreciate, but until I have them built I can't comment on the easy of typing for each style. I also need to work on the type of keycap which will work best with the design.
Hopefully I can get one of the boards made up tomorrow, although since my company has moved buildings I've lost track of the PEM inserts used to provide PCB mounting options. I'm also looking to make a couple of wedge bases to give the kayboards the lowest possible height while still giving desk clearance for the Teensy on the bottom.
On playing with them, I feel that the V2 should allow an additional double height thumb switch on each side of the OneHand (4 in total on a Two Hand) to provide a few more options without needing to drop into layers and other tricks. I had added two connection points on each side to allow a switch to be added without needing to expand the PCB size (10cm x 10cm PCBs are much cheaper than 10cm x 15cm!). I'm also thinking of tweaking the vertical offset of the outside rows to better fit my hand shape.
Finally, I'm also looking at connector options to link the two halves via I2C. I'm leaning towards either an RJ11 type connector, of a 4-pin MIN-DIN (S-Video) connector.
Now, where's my soldering iron...