Hey
I built the 10 High racks that ballpython.ca has (Mark).
I ran the tape along the back of the units, only to realize that this did not create the amount of heat I wanted in the back of the cage. My room is the low 70's also, and I could only get it to go up to about 80 or so (Dimmer at full).
So, I just got in more Flexwatt, and I put 1 foot under each cage at the back......and now I can create the gradient I want (93 and 83).
It's akmost twice as expensive because you use 10 feet of 11" tape instead of 6....but well worht it.
I have heard many people that run it down the back have no roblem at all.....but I think this is largely dependent on the room conditions. I have my snakes in my office, and the power I already draw makes it impossible to put a space heater in here to oncrease room temp.....blows the breaker every time
Hope this helps.
Rob