I have a slightly different approach to matting artwork that may interest you. Over the years, I have noticed that hot glue is very sensitive to humidity and temperature variations, and has a tendency to let go at the most inconvenient times! In my district, we do a large K-12 show in the public library, which stays up most of the summer. It is a community event, and a really big deal for this small town. The problem is that the work has to endure for a couple of months, not just a week or so. The way I handle my part is to use double sided framers tape, the type used to glue paper backings on frames. It is simply the best stuff I have ever used! The tape comes in rolls that fit into a gun of sorts (3M makes it) and applies quickly
around the edges of the paper or tag frame. I hang a lot of work-250-300, and we hang a lot of it from the ceiling of the library, so it can't be falling off on peoples heads! Much of the work is mounted on 16x20 fomecore, double sided, with colored tag covering the fomecore. Pictures up to 12x18 look great on them, and appear double or triple matted. Pictures are mounted on both sides and hung from hooks from the ceiling. The tape holds like iron, and when it is time to dismount the work, I simply take a putty knife and run it around the edge of the work, and off it comes. I have even displayed 3D work this way, by both taping and wiring the work to the fomecore.
My advice to anyone hanging a large show is to get scientific about it--in other words, standarize sizes, use reliable adhesives and mounting materials, and make sure you can get it all apart when sending it back to students. Hope this helps.