I had the same question
So I asked the fellow who makes our canopies- Jeff at Airplane Plastics. He made up some samples, and actually found one brand that works. I’ll have to go to the shop to see which one he picked - memory isn’t working yet today. Duro brand comes to mind...
One thing I did pick up from his conversation was that ‘laminating’ resin is not what we want to be using against the plexi. He told me that it simply peels off easily - his experience with damaged parts coming in for replacements - the layups peel off easily unless the builder used West System, or something similar.
I used West System when I built my 1st RV around 1990 - it is still around (2000+hrs) and the canopy attach has not let go or cracked. I assure you, that was pure luck - I did not know I was using the Right Stuff.
His suggestion was to make the normal layup using wax on the plexi, then peel it off and reattach using the West system.
How did I come to find this out? I let another fellow fly my plane, and it came back with a corner of the windshield fairing loose. Apparently, my buddy used a bit more gusto when closing the canopy, and popped the fairing corner loose from the plexi. I used the prescribed brand of isocyanate and a insulin needle and fixed things, but if it happens again, it will be New Layup Time for me. Oh boy.
At least I’ll know how to do it properly...if I can remember the process...uhhhh..
Lock-tite is the stuff you cannot get anywhere near plexi.