Construction of the ALU board is now complete and preliminary tests indicate that it works well. It took about a month to design the PCB and after getting it made by Express PCB, it took a few days to solder the parts on and get it working. That includes hooking it up to a microcontroller which I've programmed to run a simple 'torture test' to drive the board and detect errors. This test is only 8-bits and doesn't include the SB function because I don't have enough ports on the microcontroller to test the whole 16-bits in one go. But each 8-bit section is working for most of the functions.