I built a version 1 input board and it didn't work.
As it turns out, it didn't work for several reasons. One of those reasons can be found upon inspection of the back of the board; one of the traces on the output connector goes right across another pad, connecting them. Another problem was that I probably connected the board wrong. The main issue was related to communication, and specifically the polarity of the latch or chip select signal. I'll post soon with some details about how communication actually works with the chips I'm using. The important thing at the moment is that the problem seems to be mostly solved. I'm not entirely sure, though, because I think I fried a shift register.