Please feel FREE to download, share and most certainly print this simple (yet very functional) design. I decided to design this since I liked the support base for the UNO starter kit published by SebastianPelluet, which I made for a friend. I needed one for my ELEGOO MEGA2560 clone board so I measured and drafted a 3D printed specimen and re-sized it to fit my MEGA board. Its a really nice fit and it makes it very easy to work on Arduino projects without things moving around relative to one another.
For the installation of the MEGA2560 board I recommend using #2 or #3 machine screws, however any reused screws from scrap electronics might work, just try any fastener that looks like it wont split the plastic. As it is to expect the holes wont have a great tolerance if 3D printed but the pilot holes for the screws will allow you to drill or expand the holes with heat (hot needle/point) to fit larger fasteners (up to 3.2mm outer diameter is what the board will allow).
I printed successfully using 3 shells, and either 2 or 3 top/bottom solid layers, and around 25-35% hexagonal infill. Layer height 0.25-0.35mm