Obviously the glass is not totally square,so IMO it would be much better as Alvin said, to trace a pattern and use that instead.
I did this and had mine made up in 5mm Tempered green tinted glass.
I realise your glass is the smaller one,without the frame.
Shouldn't cost a bunch either!

Last edited by jockbolter50; 10/11/2009 6:13 AM.
1950 Chevy Advance Design 3100 in Scotland
In the Stovebolt Gallery
More pix on Flickr.
I've definately got this truck thing in my blood ... my DNA sequence has torque settings
"Of all the small nations of this earth,perhaps only the ancient Greeks surpass the Scots in their contribution to mankind" Winston Churchill.