The heavy duty canvas tarp was the only thing that we did not tie down. It usually went right behind the mantle. The one thing that always got me was the unsecured weapons laying all over the vehicle. First it was more weapons then any crew would be issued and they were unsecured. Securing your weapon on your person or some where is drummed into the head of every soldier.
Tom and I were in the same unit. I second what he has said, the other item that could be counted upon to stay in place was the heavy camouflage net and cover case, sometimes folded and lying on top of the tarp. Let’s not forget, the objective of most tankers is to keep the tank on the straight and level, and not have it killed off to one side, that’s the way tracks get thrown. But there is a lot of “bow to grill up and down rocking” over up and down terrain— so you don’t want stuff on the rear deck that’s unsecured. And as Tom said, each tank crew (from WWI to now) got their individual weapons, their crew served weapons, and that’s usually it. There isn’t room or need for other stuff.