Adding the corrugated metal roofing was pretty easy, but harrowing.  I chose the same stuff metal shed roof are made of.  Climbing through the roof structure to place the sheets, and hanging over the edge to set screws was scary at times.  Worse still, a 25 MPH wind kept playing with our wits. Ten feet off the ground may not seem like much unless your trying to hold a twelve foot sail in one hand and a drill in the other.  Hey wait...what's holding you on!?