I have a zoo med stick on and flexwatt both set up to the same herpstat. The probe is over the flexwatt portion, and keeps that at a constant 92, the zoomed (the desert one that gets the hottest) heats up belly heat to about 84 monitored by a second thermometre probe, on the same setting because it is designed full power to only heat to max about 95 - whereas the flex watt will get upwards of 105. I have a rack that is about 3' long, so there's half with no heat source, a middle ground, and my flexwatt on the opposite end.

The thermostat monitors heat levels by outputting less than full electricity to the device, so if you use flexwatt in conjunction with another heating method that is designed to reach a maximum temperature that is less than the flexwat, it will automatically be cooler than your flexwatt. If you're going to try this method it does take some trial and error and lots of attention paid to the temps for a few days (without the snake in the enclosure) but if you pay attention to the max heat ranges you should be able to work something out without using a dimmer at all.