I've used West Systems epoxies for a long time both on hotrods and large scale model airplanes. I wouldn't say it is exactly clear, at least not the structrual stuff. Casting resin is clear but it is not the greatest adhesive.
West has various hardners for different temperatures. They all work very well. It is tough and reasonably flexible when cured. You add stiffness with FG cloth and or carbon fiber.
As for sticking to non porous materials.....if you rough up the surface it sticks pretty well. Glass I don't think so. I use glass bowls to mix the stuff in and it pops right out when hard. Plastics work ok if roughed up very well except polyethlyene and anything with teflon. Mixing boards are usually Poly and the stuff pops right off. Sanding and roughing the surfqce makes for a mechanical bond but on wood or anthing porous it really sticks hard.
Metals....again a very rough surface makes a great bond. I have done several funnycar bodies and the aluminum body mounts are holding up very well. These things distort something fierce at high speed and often bend and wrinkle the aluminum work. The mounts still hold tight however.