I really liked Kyle's mounting on his RepBox, but I have the hinged lid add-on for easier access to the MMU itself and it would've both not fit and interfered. I think this is for the RepBox v2.3, I'm not sure on the wall thicknesses on the newer acrylic versions.
This model nips the one of the top bolt holes off, so the longer bolt isn't needed. According to the original models, you'll need: 6x M3x12 bolts and 6x M3 nuts
I ended up using 2x M3x12 through the plexiglass and 4xM3x8 through the frame only.
Note: This is not fully tested, a button head bolt may overhang and contact the hinged lid. In that case, the part will need to be extended to a different mounting hole location, or it may be entirely fine with only the bolts on the side.
The author remixed this model.