So right now I have my 320ish gram male BP in a 20 gallon long aquarium but want to upgrade to either a Vision or Showcase cage (found some great deals on Craigslist!). I'm looking into getting either a:
Vision #332 (36" L x 28" D x 18" H)
Vision #221 (28" L x 22" D x 12" H)
Showcase (36" L x 24" D x 24" H)

I know it's risky to use a Zoomed UTH with plastic cages because the temps get insanely high and can easily melt the plastic (I've even heard of them cracking the bottom of glass aquariums!), and I'm not handy at all so trying to properly install Flexxwatt tape is out of the question (even though everybody says it's easy, I'm sure I'd mess it up somehow). So I was going to go with an Ultratherm UTH, which from what I've read is essentially Flexwatt tape encased in a polyurethane material (or some kind of heat safe plastic).

What kind of tape do I use when I attach my Ultratherm heating pad to the bottom of my PVC tank? Foil tape? I'm assuming I can buy that at Home Depot or Loews, right?

More importantly, depending on what size of enclosure I buy, what size Ultratherm should I be using? Would 11" x 23" for either the Vision model #332 or the Showcase be a good size, or should I go bigger? What about the Vision model #221?

Would the Vision #221 (28" L x 22" D x 12" H) even be big enough to house my male BP for his whole life?

Thanks for for answering my questions! Phoenix is my first snake and I want to do it right the first time (and preferably buy him the best sized enclosure so I don't have to stress him out by continually moving him around).