Also remember that if your basking area is 6 inches from the top ( then the height of your cham ) and if your heat/ uvb is on top your cham depending on size is only going to be 3 inches away ?
The dowels need to be at least 9-10inches from the top of your cage, if your uvb and basking lights are sitting directly on the top, to prevent your Cham from getting burned. You actually want the lights to be a good 9 inches from your chams back
Are you now saying that your problem posed in Post #1 is solved?
If your basking site is 6" from the screen top, and you're going by that 9" guesstimate then your Arcadia T5 HO 6% UVB w/ reflector (from other posts/threads) should be 3" above the screen top.
Basking light can/should (IMO) be considered separately.