Hi there,
The UVB bulbs really don't put off much heat, at least not enough to cause a thermal burn.
The screen does cut down on the amount of UV that the dragon is exposed to, but placing it on the screen can still work.
For instance, the t5 HO reptisun 10.0 is very strong. For proper exposure, it should be around 12 inches from the basking site. Since the screen will cut down some of it's output, you will want to have it around 8 inches or so from the basking site if it sits on the screen.
Now, if you have an MVB, you definitely don't want your dragon to get close to it as they get very hot and can cause burns.
So, if you post a picture of your setup, and tell us which lights you are using, we can help guide you better
-Brandon