Heating a tub question

Hello,
I have asked many times about heating with heat tape.
I have attached a pic I drew to better explain, but pic is so bad, understand me I am bad at art haha.
So like the picture shows, I am building one tub rack with melamine wood and putting tub in those like rack system. I decided to do it to keep heat better and secure the lid. Even though sides and top are all blocked, I am going to have lid on the tub. I was originally going to put 12 inch heat tape under the tub to create a hot spot. My room is around 73~75 so I was thinking that heat tape could possibly create some heat inside the tub since tub is covered with melamine woods except open side. If it doesn't work out, I am planning to put a 4 inch heat tape on the back cool side to emit some heat to the tub, not to the hot spot. Would this work ? or should I just put another tape on the cool side instead of back cool side?\
https://gyazo.com/193adfe2d1de7638332e2864151f0ca0.png
https://gyazo.com/193adfe2d1de7638332e2864151f0ca0

You can't wire two different size heat tapes together. You would have to have two separate thermostats to run them. I'm not sure if heat tape on both the hot side and cool side would lend to the actual ambient temperature or not...

Quote:

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Originally Posted by Aedryan Methyus

You can't wire two different size heat tapes together. You would have to have two separate thermostats to run them. I'm not sure if heat tape on both the hot side and cool side would lend to the actual ambient temperature or not...

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Oh Forgot to mention, I will be using different thermostat of course. Planning to make the back heat/cool heat tape to 80degrees and belly to 90.

Any opinion or thoughs? Whether it is good idea or not