I have used plexi glass but it is not as clear as regular glass. It is easy to cut sure but if a bulb was to explode would it burn? I would get plexi glass because it is easier to cut and at present I'm broke, but it is not the best way to go. I don't vent my lights I insulate my hood so no heat excapes. Make them air tight and use a/c to control temp. Thats just me. I have read in other posts the like a 265 cfm is the way to go for a 400 watt, but Zandor would really know alot more then me.

Whats the average temp in the room?
How big is the grow space?