Adding enclosed heated underbelly. Can it be done?

I added ac/dc heat pads to the tanks (two on the fresh water tank), used a little eternabond on several edges to ensure they stayed stuck. Surrounded the tanks with 1/2" foam board and filled the gaps with spray foam. Corroplast was then suspended between the I beams just to protect the foam. It's worked great for me for the last 10 years. Oh yeah, I also added an Ultrafab 12v pipe heater down near the drain valve, then thoroughly insulated the exposed drain pipes too. So far so good!