Temp Problems - Thoughts on what I did?

[Malum Argenteum]

You could get lower wattage heat tape for the cool side and see what happens running the RHP on one circuit and the two heat tapes on the other.

I've done something like this -- I have run multiple levels in a tub rack on one thermostat channel, and used an inline dimmer to reduce the amount of power flowing to certain levels in order to maintain different temps on those levels compared to the level that the probe is on. It is a far inferior method to simply having thermostatic control on each zone that you want to run at a different temp, since you've essentially eliminated thermostatic control of the zone that's a different wattage.

As far as the heat tape itself goes, lower wattage correlates to the width, right? If I were to get a lower wattage, I assume I'd be looking for 6in heat tape or do they have 12in at lower wattage as well?

Heat tape is sold in different widths -- from 2" up to 17" (for Flexwatt/Calorique), or 3" to 21" (for THG). Most widths are available in only one wattage per foot. Some Flexwatt widths are available in more than one wattage per foot: 3" is 6wpf or 10 wpf; 4" is 5wpf or 8 wpf.

Whether to choose, say, 6" or 12" heat tape should be based primarily on how much area of the floor you want heated (especially if you're not using a substrate that will disperse the heat a little). Then you figure out what wattage is appropriate if it is a width for which there is a choice. Then you use a thermostat that's going to do what you need it to do -- either control the temp reliably or (if the tape is a higher wpf than is ideal for some reason) limit the wattage that will ever be sent to the tape (which Herpstats can do, though this is most useful in only some rare instances such as minimizing incubator temp spikes).

An interesting fact that was incorrectly (perhaps just unclearly) stated earlier here is that heat tape is adapted from underfloor heating (that's why for a long time only Calorique made it; they spun it off their floor heating); similarly, heat cable that used to be used most back in the day was adapted from gutter/pipe deicing cable. None was designed for reptile keeping, and certainly not designed for PVC enclosures, which came into use after almost all our heating hardware was established (with the possible exception of Arcadia's DHPs). Not centrally important to the discussion, really, but worth keeping in mind when a person is trying to figure out the "best" heating method, as the only thing that matters is how they perform.