Light Problem

Hello,I just purchases a kessil a360w for my 75 gallon tank. ( I know I will need 2) I a going to mount it from a cool hanging thing from the wall. I will meed to cut holes in the top of the tank to have the light shine through, and so I can lift the canopy over the lights. I run the problem of fish jumping out though. Can anyone tell me what I can do to cover up the holes in the canopy so that light can shine down, and my fish couldn't jump out? I would like to avoid plexiglass and glass. Thank you