im a bit surprised that you believe that Resonance wise glass is similar to plexii - possibly theoretically this can be proved.Physics and mumbo jubo( i havent actually checked). All i can say is that my clients can hear a good amount of differnce between the two.
Also, i do not completely agree with venkatcr that a reasonably thick acrylic sheet will snap easily by tightening. For that one has to be very stupid or very strong, maybe both. They use this stuff to make dance floors in nightclubs for people to hop n jump upon.