Much appreciated Terry! The more feedback the better.
1. Metal is certainly an option. I've never had an issue with the plastic, but you're making me nervous, so metal fasteners might be a good idea just in case.
2. Thats a good idea that I hadn't thought of.
3. A better strap would be nice, but I'm cheap, so this might be lowest on the list of priorities
4. The material is actually relatively limited. It'll be made from the scraps of sails. (my dad owned a sailmaking company up until recently) So will be waterproof, but thinking about it now, might be a bit rough. Gluing some felt to the inside might be a good idea....
I'm thinking about adding some extra, more usable pockets to the outside as well. Hopefully try to eliminate the need for the external pouch.