temperature swings are not good for a ball python. but with a on/off thermostat the swing will be like 3 degrees. if you set it at 92 with a 1 deg differential, then it'll heat till 92 shut off, and when it drops below 91 it'll turn back on, so no swings. i use flexwatt for my ball's tank. i have a 75 watt red light that i use in the winter to keep the ambiant temps up. but right now i have on the warm side, flexwatt (from reptilebasics.com) on a johnson control thermostat set at 92 with a 2 deg diff. and on the cool side a 4" piece of flexwatt on a rheostat (dimmer) to keep it at about 82-84 degreese. i am thinking of putting an old zoo med thermostat on the cool side once i get my rack. hope that helps