i used the aspen, but it sticks to everything, and you end up having to clean up every time you open the tank. also, it sucks the moisture out of everything, so humidity was an issue. i went and got two of those reptile carpets, they work fine so far.

1) they're easy to clean
2) they insulate against that hot UTH, the hottest it gets in the warm side hide (totally depends on house temp) is usually 90, and that's if its warm inside, usually it's mid to high 80's
3) for humidity, i have a large bowl with sphagnum moss, and i throw some into the two hides as well. stays moist for 3 to 5 days. i check it when i change the water. and you can rinse it, ring it out and use it again. up to 4 weeks they say, unless it gets soiled.

by having two, you have one cleaned and ready to swap out whenever the one in the tank gets messy. i suggest heavy decorations in the tank to prevent your snake from trying to crawl under the carpet against the glass.