I wouldn't risk it.
I am pretty sure that the Aussie made Sterns are toughened glass, only because I have seen a Cosmic Princess shatter into a million glass cubes when hit on the edge on concrete.
I think that maybe the older Gottlieb's are ordinary glass but I am not sure.
Toughened glass can take a fair bit of pressure on the face but hit it the wrong way on the edge and its game over.

+1. I have broken two backglasses, toughened glass both of them, they shattered into millions of pieces. One of them was an as new condition 6million$man backglass that i scored for $20 many years ago. Had it sitting against a wall beside a machine, lifted the pf of the machine, the ball fell out and clipped it on the edge 

The other a Wms SuperStar bg.. but it was stuffed anyway with a lot of missing paint. i wont say how it broke 

I wouldnt be trying to cut it either what backglass are we talking about btw??