Safety is no more an issue than gasoline. The tanks are heavy and tough. I've seen trucks hit right on the tank and not leak. If you reduce the capacity enough by denting it will vent, and the vents are at the highest point of the vehicle.
There is near zero spill possibility during filling. Both dispensers and tanks have high flow shut offs that won't allow a spill. Besides, once you remove the pressure lp vaporizes in most temps and will quickly dissipate in the air. The biggest safety concern is that lp is heavier than air unlike gasoline. If there is a fuel leak it will settle to the lowest point, and that is why you won't see lp fueled vehicles stored inside. They can be in an enclosed building for repair and maintenance, but they are stored outside. Nothing like a small leak, and then someone spraying sparks from a grinder into the center drain gutter in a shop
