Out of curiosity, what all are you trying to fit into the case, and why did you opt to stick the jack in the top of the case rather than in the corner you put your switch? Looks interesting...

I want to know how much room I could possibly make . I'm making room for 1 extra switch (same type as in image) and place for a half-speed oscillator that can be switched on by that switch.

To answer your 2nd question: I have already modded a gameboy with the pro-sound connector in the lower corner and wanted to do something different than last time . Maybe there are some difficulties that I'm not aware of...

a) Is there room in the case to add another switch (same type as in image)

b) Are there other places on the circuit board that I can cut off (did some underneath the upper headphone connector)

c) Is it a good idea that I added a headphone connector in the upper left side of the case? I didn't see it very often, maybe problem to wire, sound, space ...

Thank you