Thanks to everybody for the great info. I just pulled the canopy out of the box and measured the opening:12"*40". Not sure how I came up with the earlier measurements (oops). So now I'm thinking (with all your input) to mount three our four fans in the back pointing in. Maybe even rig up two different circuits and have two kick on when temp reaches 80, the other two at 80.5. I want to be prepared since the sump will be no help with cooling. P.S. The cat decided to check things out from the inside for me.