"If I plan on a 5 wide I guess the sheets have to go across with seams????"
You should be able to get 5 wide sheets of aluminum for a 5-wide.

My first teardrop was factory built. I was surprised to find it's roof had .063 on it with no underlying plywood. It lived through several nasty hailstorms with at least 3/4" bombs. No dents. My build from last summer has .040 on it and I'll be crossing my fingers with it's first hail storm. I'd like to hear what other's have experienced. I think some of this issue must involve the hardness (alloy) vs. thickness of aluminum.
Tony