Hey YHR you should check out grabcad.com and search for tank. You will be surprised at the results You can just scale them up to what you need, cut it into sections, and design a way to bolt/attach them together. In theory it is easy, but I have yet to see anyone make a fully printed RC (besides quads/tricopters etc) besides the OpenRC project.
It really isn't too hard to get into, my favorite part was setting up a webcam and remote commands to control the printer from work. It was always great to just log into a webpage and pull up a live stream of my printer bed. I can't wait until we get a new printer for work