Here's a drill guide if you want to use a SNES Multiout connector with a Virtual Tap on your Virtual Boy.

Dimensions are for fitting Laser Bear's Panel Mount Snap-in Multiout (check his website here https://www.laserbear.net/pages/downloads )

It fit inside the jack and volume holes of the bottom shell of the the Virtual Boy.

It's also have the hole for the palette button selector.

Check the (long) video where I use it (fast forward to 38:15):