I don't see a problem trying him out in the 20 high for a while. As long as he continues to eat then I wouldn't worry about it. Worse comes to worse you can always move him back, but I really don't think it would come to that. It's not like you are talking putting him in a huge enclosure. He'll be better able to thermoregulate, I'm guessing you are using a UTH on one side. He certainly will be able to find his water and then find his way back to his hide. With a 20 high he could even have a cool hide and a warm hide which would be nice for him. I use water bowls that are hollow underneath, that double serves as a cool hide. Let me see if I have a picture...
Here is one, that part that sticks out on the side is a "handle" to make it easy to pick them up, also serves nicely as a doorway into the "hide" area underneath the bowl. That's Fang, my Russian Sand Boa, in his 40 breeder.

Good luck with your new little guy! Do you have any pictures?
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Lyns Lair
WNY Herpetological Society
0.1 Cat (Mia)
4.2 Ferrets (Wolf, Shadow, Verdell, Sullivan, Boo, Peach)
2.0 Rats (Inky & Oy)
1.0 Carpet Python (Bear)
1.0 Malagasy Blonde Hognose (Wilbur)
1.0 Malagasy Giant Hognose (coming soon)
1.0 Yellow/Everglades Rat Snake (Pumpkin)
1.0 Russian Sand Boa (Fang)
0.1 Normal Corn Snake (Mysty)
1.0 Anery Corn Snake (Suezo)
0.0.3 Eastern Milk Snakes (Uno, Dos, Tres)
1.0 Ball Python (Slytherin)
2.0 Smooth Green Snakes (Fred & George)
1.0 Northern Water Snake (coming soon)
0.1 Golden Greek Tortoise (Sunshine)
0.2 Mississippi Mud Turtles (Squirt & Shyanne)
1.0 Green Iguana (Norbert)
1.0 Bearded Dragon (Moose)
0.0.1 Mountain Horned Dragon (Tiramasu)
0.1 Oustalets Chameleon (Cera)
1.0 Whites Tree Frog (Trevor)
1.0 Solomon Island Eyelash Frogs (Gimli)
1.0 American Toad (Bump)
1.0 AFT Gecko (Cocoa)
5.5 Leopard Geckos (Trouble, Scooter, Simba, Firenze, Teddy, Mystique, Freckles, Dotty, Zipper, Twister)