Sasha, I've never seen mini DIN's on musical instruments. I guess that there is no difference in performance so It's only an aesthetic choice and the need to make cables that would fit. Most of the time I like things to be packed in small as possible and understand your stand on making the SEQ as slim as possible, At the same time there are some parts I prefer large (or normal) as the smaller ones seems to me funny on instruments - as such I would never use banana plugs instead of 1/4 jacks although it would save me panel space, DIN is a new world for me but I guess it's the same. Back to the real subject, your SEQ, a few more questions might trigger an idea. How exactly are the two boards connected, I see the space for DIL connectors, are you adding them on both and then connect with a jumper/terminal between them ?