Rack heating question

HI was wondering if anybody is using back heating in there rack system, and what temp u keep your thermostat to heat the back of your tubs. My tubs stay heated about 88 in back but have to keep my t.stat at 95 to meet the 88 degrees.

I tried back heating for a while but found that I had to crank up the thermostat to get the proper temps so I finally added belly heat. I think it would work fine in a warm room that is kept at around 80F, but I think it's a bit difficult to heat the entire cage using solely back heat in a normal room that fluctuates regularly.