I'm working on a commissioned gameboy mod in exchange for artwork by the fantastic pixel (and other ) artist KeFF. He requested something that, to my knowledge, has not been done before - two 1/4" jacks crammed into one original gameboy. The challenge is that a single 1/4" jack is generally squeezed in where the power supply is placed in a stock gameboy - then a ribbon cable is installed, relocating the power supply to the opposite side, in a smaller cavity. To install two 1/4" jacks, both of those spaces must be made available.

My solution:

By splitting the power supply in half and connecting the two halves with ribbon cable, enough room is made on each side for a full length 1/4" jack. It's definitely a squeeze, but everything functions.

As a bonus, the jack on the left is wired in stereo, allowing the option of a stereo cable, or a mono cable (grounding out the right channel, which can be accessed via the other jack).

Still to be done - wiring up the variable speed control and a switch, which I'm honestly not yet sure where to put. Those jacks take up a lot of space.