I broke the plate into 2 pieces to allow for printing on smaller 3D build platforms (solid model also provided).
You can use the free 123D app available @ http://www.123dapp.com/123d and download my file @ http://www.123dapp.com/123D-3D-Model/Arduino-Mega-Plate/605944 and create your own rapid proto plate/box for your Arduino Mega! I also have a write up on general 3D printing at home here: https://www.instructables.com/id/Basic-workflow-for-3D-design-in-Sketchup-and-3D-pr/
Now you can send that beautiful $55 board out on your next physically aggressive project with confidence. I also built in a sliding trap door for lower plate egress as well as top box openings that help extend your leads to sensors, motors etc all while protecting your board.
Oh, and if you run an Ethernet shield I have included a box top that can house both boards perfectly.
Oh, oh, and if you run an Uno check out my Uno Protection Box here: https://www.instructables.com/id/Arduino-Protection-Box/
Let me know if you have any suggestions on the build and Make On!