I recently have second guessed myself at my Ramses' setup. I have him in a 30"x12"x12" glass tank with a red heat lamp to warm the hot side during the day and a reptile blacklight for night time use. He's just a little guy still, at a 141 grams and about 22". I put the UTH on the end of the cool side and have it all controlled with timers and a rheostat on the heat lamp. My temps are near perfect from what I have read: 90-92 on the warm side during the day, 84-86 on the cool side. 80-81 on the warm side at night, 77-78 on the cool side. I also monitor the upper end of the warm side, and it stays about 5-6 degrees warmer than down low, so if he wants to bask, it is warmer as he goes higher.
My UTH is on the end of the tank, however, not below. I did this because that was the manufacturer's recomendation (Zoo-Med UTH). It said to use the UTH as a secondary heat source and not the primary.
When I take my litttle guy out from his warm hide, he is always nice and warm, evenly throughout his body. So should I change my set up? Do snakes need the underneath heat for digestion like iguanas or something??? Any input would really set my mind at ease!