Congratulations on your new carpet! They're awesome snakes! It sounds like your temps are good and kudos on the first successful feeding. I agree that the RHP should be sufficient without the UTH. As far as enclosure sizes go I like a good combination of floor and vertical space. The 36x24x18 is a good fit for now and either of the 4 footers will work later. A 4x2x2 is a really good size for most adult carpets imo but bigger is very cool too. Only one of my carpets is active inside his enclosure. Most of them are usually perched on a branch or shelf and all but one will use their hides. I started out with colubrids, that I later rehomed, so I still have some of mine in T8s and T10s with shelves in them. Those are adequate but I plan on upgrading them after I get caught up on my 8ft enclosures for my Olive and Scrub pythons. Best wishes with the new addition. Share pics when you can!