I looked at this a bit further, and there's a small difference between the Mac 128K/512K ROM socket and the Plus ROM socket (beyond the difference in space between chips on the motherboard). So even if you could cut the adapter board in half, it still wouldn't work in the 128K/512K. Fixing it should be pretty simple, but it means there can never be a universal adapter board that works in all those machines. There will need to be a version A for 128K/512K, and a version B for Plus.