Barry, this was back in the late 70s that I was sticking veneer to plexiglas. The adhesive I used was from a plastics supply house and was a stinky three-part concoction called PS-18. They also sold a two-part (?) chemical called PS-30 that wasn't quite as good. Nowadays, I have no idea what is recommended, but I'll bet the adhesives technologies have come a long way.