This is going to sound a little crazy, perhaps, but I built ammo crates for the Academy Merkava II, and I built them out of wood. You can use balsa, although I think basswood is a little better. Real wood is the most convincing.
In the near future, I'm planning on building the Italeri Opel Maultier with the flak gun on the back. I plan on removing the plastic bed with its sink holes and ejection pin marks and replacing the whole thing with wood and Plastruct angle and channel "iron".
Gip Winecoff