"When it's 39* outside and the paint booth is sucking the heat out of the building, this is how you keep the temps up to a balmy 75* in the paint booth.."

You have that problem too? I try not to paint much below 40 deg either. I always try to find the balance between sucking out fumes and keeping the shed warm. I am thinking about mounting my exhaust fan down by the floor instead of up by the ceiling. I'm not sure it will make enough of a difference to do it though.