You will get much more enjoyment out of your Carpet if you go with the tallest cage possible. They love climbing and perching. Given that, the T-5 would be the best of what you listed.
I have an A-25 on order for my Jungle. It's a 4x4. No perches were offered by AP, so I got 2 shelves and I will rig up some perches as well.
I ordered both UTH and RHP though I don't expect the UTH to get much use. But for just a few bucks I figured that I would provide the option.
I had them groove the cage for LED lighting since I will have to mount my own being that I want multiple color lighting options rather than pick just one of three colors that AP offers.
I'm glad to hear that you are moving your snake to a more arboreal one with much more freedom of movement opportunity.
Esmarelda, Jungle Carpet
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