The CHE emits heat without light so your dragon can get quality sleep at night. I have read they don't go "all the way to sleep". As long as your viv stays above 65 at night, you don't need anything. Most important, heat and UV; heat for digestion and UV for vitamin d3 synthesis. I am using an infrared to supplement the ambient temp during the day in addition to the bright white. Your basking spot should suffice at 101, but you want to use a bright white light so they will squint their eyes or close them so they don't develope conjunctivitis. Put your UV light along side the bright white so he gets uv while basking.
As for the repti-sun 10.0, you lose some uv through the screen, but your dragon will still benefit. I have read a number of places where 6-8 inches is optimal, so under the screen would give best exposure if your fixture is not that thick. In my viv I have a 48" repti-glo 10.0 where the manufacturer claims exposure up to 20" away. My dragon has exposure ranging from 18" at the greatest distance from the bulb to 8" at the closest on the upper level above his cave.
I worry about my Dragon too, but there is a lot of data to support the 6-8" theory for gaining maximum exposure. When Nero was in his smaller tank (which I now use for feeding) The light was on top of the screen on the half that does not flip up and it was fine. If you want to mount it below the screen, get a small piece of wide flat wood (about the size of the light fixture, and run screws through the screen into the wood so that the screen is almost screwed to the wood (you are talking about the metal mesh screen on the flip up tank lids right?), then leave about a 1/8 inch gap on the screen side and slide the mounting holes over the screw (provided you marked their location first) and that should hold it just fine. As for the cord, you will need to provide the smallest exit hole for the cord as possible and maybe use something to weave the cord hole closed around the cord.
