You only have 18cu.ft. in that box. A 240 cfm fan is overkill, so most likely your problem lies elsewhere.

The Intake you described kinda sucks. If you could raise the cabinet a few inches you could put a 90 degree elbow coming out the bottom and then hook you intake fan etc to that.

Improving your intake is your next logical step.

My temps get into the mid 80's every day and my plants don't seem to mind. But that bepends a lot upon the strain.

PC :smokin: