I reached out to my contact at LaSalle Bristol regarding their ThermaHeat RV Holding Tank Heater Pads like # 277-000164, and she did say that the pads should be applied to the bottom of the tank and should not be subjected to any kind of pressure or compression. Compressing the pads like you described would not allow for proper operation and may even lead to damage.
Your best option for using the pad will be to try and add some spacers between the brackets to relieve that pressure that... view full answer...
The Classic Accessories Deluxe PolyPro III Heavy-Duty Cover for Class B RVs part # CA80104 only weighs around 20 lbs so it won't be hard to lift up onto the vehicle for installation. view full answer...