I was inspired by someone describing making yogurt on the trail -- he did it with an insulated dark bag. So apart from the yogurt making part, I have a bag with some reflectix material inside, but need to decide how to close the top of the bag to keep more heat in. I was thinking Velcro glued on with something -- except, what? I have some Speed Sew I could use -- do people have any experience with that? Would it hold Velcro on thoughout use? Any other glues that might work better?