Glass is the dogs bollox over perspex! I tried perspex once for my beardie viv's and the whole thing is nackered! its get scratched and warped with the high temps..
As for glass and boas I think its worth tuffened... I know people who have had there boa smash 4mm glass with ease. go fpr 6mm and tuffened.... cost alot more but its worth it, especially for me as i have guinea pigs running about! :shock: