So I've decided since I have to build he roof again anyway, I might as well take crawler07's advise, and build a wooden buck. The buck I've made is a simple one, and I built it out of 1/2 inch balsa. I don't intend to hammer against the form, just use it as my guide. I've annealed my brass before starting so that I don't have to heat against the wood either, not a good idea with balsa, my wife would kill me if I set fire too it. Here's some shots of the basic wood form
It's a nice dock isn't it
Cut to general shape
Now this picture shows the height of the buck, the buck it self is 1.3cm tall (when I scale I use centimeters and millimeters, one cause I'm Canadian, and two it's easier then figuring out thousandths) this happens to be the exact scale height of the roof after it slips onto the cab, so as I shape the buck, I will have to keep this in mind
I'll post more pics as I go