When printing the original, I found it worked well for sheets similar in size to the one for the MK3 (unsurprisingly). However, for my XPlus-3, I have a 280mm sheet, which is a bit too big. This meant it would either not fit, or if I spaced out by one more cell, barely stay in place.

To fix this, I made a quick hack by cutting the ‘feet’ that hold the sheet from the base and bringing them right to the edge. These can be used together (as I did in the image) or combined with the original, allowing you to securely store more sheets.

I don't have the source file(s) for this: this was an STL kludge I did in OrcaSlicer.