Young snakes are very vulnerable to a wide range of predators, as Snowman alluded to. They spend their time trying to get the occasional meal without being on the menu themselves. They do not like open spaces as a result. Once they reach a certain size this is no longer so much of an issue and they are happy to wander further afield. With the larger enclosure, unless you fill it up with rocks and logs and branches etc you will still have the same problem, especially where at least one side is glass. You could try keeping it full time in the click clack it came in for a week and see if that makes any difference to it feeding.
My personal preference for heating pythons is to provide bottom heat as the primary heat source. A 15W heat cord under a slate or ceramic tile with a thin sheet of MDF underneath with routed or saw cut channels for threading the heat cord into is the way to go. Placed in the back corner it requires a hole only a few mm in diameter to thread the cord through. You can then adjust the amount of cord in the enclosure to obtain the required temperature. You can use a thermostat if desired but I know of a couple of keepers that run their entire collections in this manner without thermoststats and have had no issues. They do periodically check temps within their cages as part of their regular maintenance.
I would advise against using the plastic backed tile. Plastic (and wood) are good insulators of heat. Plastic can also melt and is flammable. There is the possibility of heat being trapped and temperatures building beyond what is anticipated. Slate and ceramic, on the other hand, are fire proof and reasonably good conductors of heat. This means they will spread the heat evenly across their surface. These materials also have a high specific heat, which means they take a lot of heat to warm up. The positive to this is that when a reptile plonks its cold body on top and starts absorbing heat from the tile, the tile will not go cold in a hurry. It will continue to supply heat with little temperature change as the reptile warms up.
My advice is to tell a little white lie. Go to a tile place and pick out a tile you like and ask if you can purchase one tile because you are going to tile a room. Invariably they will say help yourself and will frequently offer a few more free samples.
With arboreal pythons, the addition of a heating bulb near an elevated perch, be it branch or shelf, is often appropriate. It depends on the thermodynamics of the enclosure – basically how much heat is trapped at the top.
Stimmies do climb – usually over rocks but also over low logs and branches. I would recommend a forked branch or two with a decent diameter and a bend in them. That way they sit like a tripod with an elevated centre.
Pythons are essential nocturnal and hunt at night. This is why feeding them after dark is recommended. It is, however, not essential to do so in captivity as they quickly learn to take food regardless of the time when offered. They will, however, be at their most active after dark.
That will do for now I think.
Blue