The RepRapPro Tricolor Mendel uses two Melzi controller boards, mounted by default on each side of the frame.
Rather than go with this arrangement, I decided to modify the existing Melzi Box design to allow you to fit two Melzi boards in the same box.
The bottom is made tall enough to fit two boards stacked on top of each other, and the top part has the key removed so you can access the MicroSD slots and USB ports without removing the cover.
Top was upside down. Flipped it around and re-uploaded the Top.
Changed the Standoffs to add a recess for an M3 nut.
One of the clips on the Top piece snapped off really easily, so I modified the Top to make the clip walls a little thicker (2.0mm vs 1.5mm).