Hey, I also have a 20 long for one of my balls. What I did was get 2 UTH's and the ReptiTemp just like you have. I got rid of my heat lamp and covered the entire screen with aluminum foil with the shiny side facing down. Poke a few holes in it, and if you have a large water bowl it should EASILY keep your humidity up. I used coco bark for bedding which keeps moisture pretty well. It's also good because when I do spray it during shedding, the humidity will stay where I want it until I open the top and let some out. Hope this helps. Good luck!