I used to have 1 UTH and 1 heat lamp. I got rid of the lamp and put another UTH (both are 5x8) under most of the waterbowl, with the rest under the warm side. I also put aluminium foil over 3/4 of the top of the cage.

It works perfectly. My temps and humidity are now perfect and stable! The heat lamp just drys the cage out too much and seems to make it hotter on the cool side than it should.

Good luck! I know it was frustrating for me at first but now it's all good