Follow the ribs on the way up. Should be a series of rivets going up and over. those are your load bearing points. Don't go out on the ends - stay off the end caps!
I took a half sheet of 1 inch polystyrene. 1/2 was a cushion for my ladder on the side, and I sat on the other to spread out my weight and prevent me from scractching somethign with my boots.
If you're really worried, just tow it out here to the East Coast and I'll give you a couple grand to take the furrow off your brow...
Just kidding - Congrats.