The method I use is two UHT's and one overhead ceramic heat emitter, and two thermostats per enclosure.

I set it up as follows:

One UTH under the cool side, one under the warm side. CHE mounted centrally above the enclosure.

I use two Alife thermostats, one to control the cool side (thermostat set to 82) one to control the warm side (thermostat set to 92).

The probes are burried in the substrate over the UHT's.

Being as one Alife can control three heating devices (all to the same temp) I connected the overhead CHE to the warm side Alife unit, so it clicks on / off with the warm side UHT, I find this keeps ambient air temps in the right range.

We use 20L Critter Cages at the moment while both are snakes are small. These have a mesh top - which is bad. To counter the loss of heat and humidity we do the following:

Get the local plastics supplier (S&W Plastics) to cut a piece of plexiglass to cover the mesh up top. with a hole in the center that I mount the CHE above. Directly below this hole I place the water dish. The combination of the heaters + CHE + plex + thermostats means that we get a set up with air temps at 78-80, cool side belly temp of 82-85, warm side belly temp of 92-95, and a stable humidity of 55-65%.

We use aspen as bedding, we tried cypress mulch for a while, and found that it is GREAT at increasing humidity, so much so that it was hard to get it under 80% lol, so we decided on aspen as our bedding of choice. During shed we put in some moisted spagnum moss, and now we'll also add some cypress mulch (we have a big bag of it) to keep the humidity at 80% during sheds.

I check all temps using a IR temp gun for belly temps, and we also have a Flukers combo digital temp / humidity gauge for monitoring ambient air temps and humidity levels in each enclosure.

When we upgrade the enclosures in a few years once our snakes have out grown the 20L's there are in now now we're going to go with vision cases (or similar) and probably splurge on Helix or Herpstat controls, as these are much better with proportional heating control, as opposed to the on/off of the Alife units. But for the price (about $27) the Alife's are working well for us at the moment

Hope that is of use to you