Yup, it's totally fine by me to trace a pattern and pass it along after you're through.
I recommend using sintra to build most of the pack now, though. I'd rather use poster board and styrofoam, since I need something that weighs 3 pounds

, but if you don't mind doing the harness thing, sintra, with very minimal amounts of bondo, will be faster. Keep the amount of bondo to a minimum, though, because bondo cracks and you can easily end up with a 30 pound jet pack if you slather that stuff on. After we move and get set up again, I'll make a sintra one and re-do the tutorial for it.