Ok so I think you could do a few things. The problem with the wire rack is the heat escapes in all directions, what you want is for it to be directed towards the tub and snake. Get some "Reflectix" insulation and place it under the tub with the heat tape/UTH on top of the "reflectix". This will make sure all your heat is going up into the tub and not radiating in all directions. Next, it looks like you have a thermostat for every tub? As long as the heat tape or UTH is the same wattage you can plug in multiple UTH or heat tape strips to the same thermostat. what might work for you is run two thermostats....one connecting all the warm sides, and the other regulating all the cool sides. You can daisy-chain the four warm to one stat and the cool four to the cool stat.

Hope this makes sense and helps.