I did the same thing as you Chris , cardboard then plywood , it took forever to get the roof profile done ( the starbord side was a little dif from the port ). The reson for cad is the lazer machne needs it, ….very easy to e-mail it to steel conpany. On other hand it took for ever to get all of that into a cad drawing , I had to measure up every inch across from a straight line , i think it was around 90 numbers for the roof profile. The rest is downhill !!! im still working on the bottom side profille, and lightning holes and thinking of incorporating a beer bottle opener ~ BOD with a useful tool .