Glass and Mirrors - cutting light panels

I'm not sure if I'm in the right forum or not but here's my question. In my kitchen I have a small "drop ceiling" which has clear panels and flourescent lights above them. One of the panels cracked and I bought a new one. I found out that the broken one is a little smaller than the new one meaning I will have to cut the new one. Is there a particular way of doing this? Its a thick, hard plastic. I was thinking if I sawed it, it would crack around the cut. Or maybe score it then break it? Please help.

PLASTIC FLORESCENT LIGHT DIFFUSERS CAN BE CUT EITHER WAY, BUT FOR BEST RESULTS TAKE IT TO A GLASS SHOP. THE CHARGE WILL BE NOMINAL-PROBABLY LESS THAN A SCORING KNIFE