The following is for those that have a Boxy Pixel Game Boy Color Shell and a 3D printed adapter for the Freckleshack, stock screen adapter, or Mcwill screens.  The stock plastic power switch will need to be trimmed so it will slide freely when installed.  This guide is NOT for the AGS-101 screen.  

The side opposite of the 'wavy side" will need to be trimmed as it is too thick.  There is a channel in the aluminum rear housing, and the power switch is too thick.  Thinning the side opposite of the "wavy" portion of the switch will allow it to fit properly.  See images below.

Below is a stock switch.


Below is the switch AFTER trimming.  Careful not to cut the two small protrusions.