I like using the premade ones in my display type enclosures as you can see most are water proof and most display enclosures require them to be put inside the enclosure due to a thick wooden or plastic base. Then I put a thin sheet of plexi-glass over it.

As for a tub I would use flex-watt. You can get the materials and make an 11 X 12 piece of flexwatt for around $10-$15. All you need are some simple hand tools that you probably already have.

I don't know what brand of 32 qt tub you are getting, but I do know you can build a slide in and out box that surrounds the tub on all but one side for about $20.00 maybe $25.00. This really helps maintain tempuratures a lot better and may be something to look into.

Ranco is the minimum I would use as well. I also like to use these as back ups to my herpstats just incase. While I have yet to experience a herpstat malfunction, I sleep better knowing I have a back up in place. For around $100 to $150 I could build a nice little system for housing one ball python and this would include a Raw Ranco that I would wire myself.