We carried ours rolled on the outside of the tracks, with two or three poles inside, until we found out that an RPG that hit a roll so carried worked better than one that struck bare armor. After that, we carried them rolled on top. Same deal with the Sheridans.
The real weak point of the M113 was the plastic bag hung between the driver's side interior and exterior wall that served as the fuel tank. Hit by a PG-7 rocket, or the more common RPG-2/B-40 they went up in a fireball. The Diesel M113A1 was a much-appreciated improvement over the mogas/ gasoline Chevy engine versions.
Some of the Russian BTR 80 and BMP troop carries seen in Chechnya have been carrying sections of pipe, sometimes filled with water, on the sides. Since the wheeled BTRs have their crew exit doors on the sides, that's unhandy, but the crews and troops ride on top, anyway, due to mines. The bigger MTLB and tank-derived APCs sometimes have fuel drums slung alongside. Interestingly A RPG-7 hit on a 55-gallon drum full of Diesel usually doesnt ignite, though it sure leaks good.
