My rack idea, comments?

[John1982]

Also, is back heat what I was referring to in my original post?

Yes

I'd like to do whatever would work best with not regulating the tape. Right now I have rocks in the tub above the heat tape so it's not too hot

I don't recommend using unregulated heat tape in any way, shape or form. If you don't want to get a thermostat your best option for a rack build would be something like the ultratherm pads. They produce heat but stay cool enough to be used without a stat. I've used them on stand alone tubs for years and they work great. Providing a link for you.

http://www.reptilebasics.com/ultratherm-heat-pads