So! I built two of the carts today, and they work fine! I'm pretty, to use the UK term, chuffed! (Is that right?)
Just one more layout error noticed - the 74LS00 is too close to the hole, to mount it in a shell I had to trim the post a little bit. (It's a bit snug anyway, but I didn't mind that).
So I have the parts to build 5 of these.. any interest? Say $55 inc. shipping to the US, $65 outside the US? (Will include recycled shell, but I won't peel the old label or provide a new one, hehe. )
Those with interest note that these are prototype quality boards with no solder mask or gold coat on the pins (just means the pins may wear more quickly and MAY oxidize more quickly). Parts are a combination of new and recycled and the warranty lasts until the moment I put it into a box for you. But I'll certainly test before shipping. Comment if interested?
And if you want to make your own, this archive has the source for the menu, a build script, the patches (you still need your own ROMs), source images for the menu, the PCB file (ExpressPCB - should have all fixes noted, though the fixes are not tested) and a copy of these blogs for documentation. Enjoy!