Heat Tape Question

I will be building some racks this year and I was wondering about the heat tape. The racks will be for ball pythons mostly, with a few of the hatchling racks being for the corn snakes. I intend to use back heat and just attach the flexwatt to he back panel of the rack. In a rack that is 3 28qt tubs across, is it best to use two strips of 11inch or 2 stripes of 4 inch? Same question with the hatchling racks. Should I go with wider heat tape?

I suggest belly heat which will help maintain cool side temps as well. Back heat has a tendency of not giving proper heat and needing a t-stat set high to achieve a 90.