I designed a tanker attachment for use with Somerandomguy03's M.A.X. Truck https://www.thingiverse.com/thing:3214824
The "rib" for the front end cap will catch the front drive wheels, but will just ride the tread enough to roll the wheel.
Print 2 end caps, and use 4x M3 x 12 screws to secure them to the center section.
The length will be 0.5 cm further to the front as I modified the end caps after printing the center section and didn't reprint the newer version that is longer as the original end caps were shortened as well.
Use supports for the end caps, but you can leave them on the end caps for assembly