I find the bottom mounted battery on the Euro Tamiya trucks to be pretty annoying. When I mounted a Lesu planetary transmission I finally had room to put the battery up in the cab.
This project includes a battery box with a replacement for the cab catch. This allows the cab to rest on a part on the inside of the cab and allows latitude to mount a different transmission that may interfere with the stock cab catch mount.
The top radio mount plate (the large flat plate inside the cab that mounts to the frame rails) needs to be modified slightly to lower the tow mount holes and lower them to the same height as the mount holes for the front mud flaps. Its obvious when you print the box and attempt to attach it to the plate. I just used a dremel and cut off a bit to the correct height.
This will also fit a stock Tamiya 3-speed transmission if you dremel off the top screw hole mount on the transmission casing.
I changed the battery box to include slots for adding velcro straps to secure the battery when the truck is in a non-horizontal state such as being carried.
I added an additional box if you don't need to relocate the cab catch.
In another project I have a relocated shift servo mount to further accommodate the Lesu (part number F-5011) transmission that I installed.
The cab catch needs supports. The battery box should print without them just fine.