New enclosure questions

[Overkill]

I'll soon be rebuilding my snake enclosures, and on my burm enclosure I'm planning to make a foam/hydrolic cement natural looking background for the back and one side wall. As part of that, I'm thinking of adding a cave to serve as his hide. One side of the cave will sit flush with the sliding door, so I can get him out if needed, but with it closed he should feel very secure. My question is if I should build the cave into the warm or cool side of the Enclosure? If it's on the cool side, I'll build it so the water tub can sit on top, and honestly that would be my preference, but from everything I've ever heard about our ball pythons, they prefer it on the warm side. If the hide should be on the warm side, I'll set it up as a basking spot on top.