If you go with PVC which IMO you should get the t8 and divide it in half till he's bigger.
Second forget animal carpet it's crap holds mold and creates issues. He won't burn his/her belly if you Spoil as you intend by purchasing a thermostat to regulate hot spot.
As for ambient with PVC enclosure you can get a RHP(radiant heat panel) for PVC and this eliminates. needing a flexxwat on bottom. But you will need again a thermostat to controls heat. Once he's bigger take out the middle piece add another few decorations and your set. As many say if you are to cheap out on stuff. Never on the thermostat as that is the best investment for your snake. Best of luck
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