Help with heat tape

[JMcBee]

I have this rack I purchased and need suggestions of heating for BP’s, I have 10qty 12” pieces of heat tape that I had applied to the back but there was a lot of heat loss with the 1/2” gap on the back, I have a 6” piece of tape also that’s 5’ long but it still leaves me with the gap on the back of the rack. Can I put the 12” pieces flat on the bottom of each rack to heat tubs individually? And yes I do have a thermostat.