flexwatt should be kept at or under 95, and your probe should be taped directly to it. You may need to elevate and/or insulate your rack if your room temp is under 80 degrees, otherwise your cool side temps will be too low.

I also got an oil-filled radiant heater and have that placed about 2 feet from the front of my rack. It's set pretty low, and heats my rack to 82-84 in front, and doesn't heat up my whole apartment.