Good call with the ReptiSun 10.0 instead of the PowerSun. I haven't ever used a PowerSun, but I hear they aren't good for beardies' eyes.
Here's a thought, although I know you already ordered a screen, but you can use a $2 window screen from Home Depot that is big enough to cover the top of the cage, or even bigger, and rest it on top of the cage with something heavy (the lamps will be heavy enough) on top.
98*F is great for a juvie or adult. I'm assuming you have a baby, then.
I bet that wasn't much help; it took me ages to fool with all the heating and I still haven't figured it out. Lucky I have a week to figure things out before my darling boy arrives.
My best advice is to keep at it; fool around with all sorts of lighting/heating combinations and wattages until you get it right.
It's a hard process. Don't forget about UTHs and CHEs! They can help a lot towards temp.