While making a pepakura armor or helmet, have you already though that the joint you made wasn't really reliable? Here's a tip for you! Use your hot melt glue gun, and use it as a pen, take the tip, line it in the middle of the flap - corresponding face joint, and squirt just a little bit of glue! It will make a really good joint, and you won't have to use your tape method, that gets messy and ugly! And also, I'm almost sure that the hot glue will not interfere with your fiberglass or resin! Thanks again and BYE!