I have found that a combination of 1.6mm mild steel and 8mm macrolon is virtually impregnable. The only time the lid on Mighty Mouse has been pierced was by Matildas disc.

It has taken a full blow from Thor and sprung back into shape, and 8645t had three free shots with his axe and only cratered the surface.

The 2 materials are not bonded though, they are just bolted (csk m6 screws and nuts internally) this gives an amazing amount of flexibility. I often have to flatten dents out of the steel substructure but the polycarb is only scratched.

I have currently run out of macrolon and am using a sheet of polycarb, no idea of the make or spec, it came from a telephone box. But, although it is slightly more brittle it is no less effective.

Trev