Cutting glass for sequencing plates?

[Roopie Toops]

The glass plates of our sequencing rig have been very badly chipped 
at the corners. New plates from the supplier of this rig are 20 pounds 
per plate. So, we got 5 sets cut locally (10 plates) which only cost 
about 15 pounds, and the glass doesn't chip. However, it seems that 
the glass warps rather quickly, and it becomes increasingly difficult 
to pour a gel without bubbles, and for the gel not to smile when 
running. Does any body else get their own plates cut, and if so do you 
use a special kind of glass? or any other tips?
Thanks, Ruth.