Heat tape or UTH?

As I've mentioned in thd past I'm in the planning and gathering stage of setting up a 75 gallon naturalistic terrarium. I have got just about everything planned out except for my heat source. In the past I have used a simple UTH with heat lamp setup. The only problem with that is that with my naturalistic setup I will have at least 5-6 inches of substrate. I have thought up a couple different ideas on how what to do, and have some questions.

-First off, with that much substrate will an appropriately sized UTH work?
-My second idea involved attaching a UTH to the backside of the tank at the hot end with a piece of reptile carpet between the heater and the glass to prevent burns.
-My final idea involved using heat tape around 1/3 of the tank about an inch or two below the surface of the substrate.

Are any of these viable and most importantly safe options? And if so, which is the best way to go?

I'd go with flexwatt, it costs less and works better. Just make sure that it is hooked up to some sort of thermostat.

I would use paper or corrugated wrap as a substrate, but 1/4 inch of aspen or Eco-earth would work as well.

Any and all UTH's or flexwatt should be outside of the cage. Back heat doesn't work well I'd stick with a UTH or flexwatt covering 1/3 of the bottom of the tank on the outside. This is a well tested and if you are using a thermostat is the safest.