The report which got me interested in this potential problem, is on page 74 of May "Pilot" mag, in Safety matters. It's just possible that all those worthy bodies CAA, JAA, PFA, BMAA, not to forget the French GSAC, just may not have thought about it.
If I can get hold of a scrap ATL canopy, to attack with various implements, the Perspex / Lexan question would be answered, for me at least.
Meanwhile my battered bit of Lexan has succumbed to a sharp pointed hunting knife, but it took more time than I would wish to be upsidedown listening to avgas dripping!
Would be interesting to have an engineers opinion.
MG