I have had some trouble keeping the GH temp uniform. I have 3 smaller fans running 24/7, but still see a top vent open and find the heat is also on. The top vent is controlled by a Bayliss auto vent, and the 20k propane heater has it's own power free thermostat that can be set down to 60*F.
I took a small turbo type fan and put it on the floor pointing straight up in the middle of the aisle and seems to have helped a lot to help keep the air from standing from hot on top to cold on bottom. I haven't seen the heat on with the vent open, and the vent seems to be open less.
