May I offer three suggestions?
1) decal silvering: common problem that really mars the final appearance. Google how to fix this. Very easy to correct
2) Heavy chains. On WW2 AFVs only seen on some prewar heavy French tanks. Not used generally b/c vastly inferior to tow cables. Need to have hooks attached -- not useful. Your use would have been very difficult for the crew to use.
3) a full 50 gallon drum would weigh about 400lbs. Lashing them on engine decks just doesn't make much sense. You see photos of some AFVs hauling some for long road marches. But then they are VERY secure. Yours would roll off. Unless they were barely filled. But then why would barely filled drums be lashed onto a deck? Also fire hazard? Use logic when applying stowage. If you were going off-roading with your friend in his pick up truck, how, what, where and why would you strap items onto your vehicle?