I took the model from RobRoy, a single fueltank/car box, and copy/past another one, glued them together in TinkerCad en made it fit my TRX4 Landrover Defender's roofrack. That's all I did.
The model from RobRoy had a lid and holes to screw it to a frame. The dual tank I made has no holes and no lid. Keep that in mind.
TinkerCad named the file Frantic Armor. I didn't. But I like it.
The author remixed this model.