How much substrate do you use in your Leo's cage? If you have too much substrate, the heat will have trouble reaching the top (especially if you use porous substrate like wood or carefresh). Just use less substrate, and it should kick the temp up a bit.
I use Calci-sand and I guess it conducts well or something, but if I don't use a rheostat inline I can hit the 100s easy. Babies I keep on tissue, so it's pretty much directly on top of the UTH, so it can hit high temps pretty easy (dangerously high).
I use those sealed flex-watt type UTHs if you're wondering, like the Cobra Heat mats from T-rex, or the Ultratherm heat mats.
-13mur 6