that is pretty fricken awesome man, yeah i remember it so clearly in the movie that both straps connect to another strap from the left side, if i watched the movie again id get a screenshot or picture, spideys my fav character because of his skateboarding aha, years of skating myself, thanks for all your info, and your ideas to replicate.
im also pretty sure he used a navy slacker jansport, not an original navy one, he just took off the diamond on the bottom right side, and added on straps.