I decided not to use the bank stick design and went for the 8 eeprom setup as an internal memory board.
If i understood the design correctly that gives me 1056 internal patches, my old yamaha FX500 has only 30 user memory slots for patches which is very poor for a commercial product , even when it was produced..
The 4 Audio INs are “nice to have” for some experiements, but no must. You could also place them at the backside.
I’m missing the AOUT port!
Sidenote: in the meantime my MIDIboxe SID/FM and SEQ are stuffed with a special DIN socket for the AOUT, so that I can use it as “breakout” box. I’ve used a 6-pin socket, the remaining pin will be used later for a serial connection to a (planned) 8 x gate extension (it’s just a 74HC595).
Reichelt Part # for the socket: MAB6
(the picture shows the 5 pin type, I mean the shading at the right upper edge)