As stated water is about 8 pounds so it would probably damage the roof. I have a 60 gallon bladder and it works fantastic but you’ll need a trailer or something. It folds up and fits in a 1’x1’x3” box. I’ve filled it full on a utility trailer and filled partially in the back seat of a pickup and also partially filled it in the bed of the truck with a bunch of other stuff in the bed that it conformed to. The material is very strong. I bleach it lightly for storage. Its surprisingly stable when its filled on the trailer and I expected it to want to roll around like a big blob but it didn’t. Im sure if you maneuver sharply enough it might roll