nope, i don't worry about it at all. the 6 inch area is slightly to the side of the uvb, so even if he is up there all the way it is not 100% direct. his usual hang out spot is in the 12-15 inch range. as for the coil you had earlier, the issue there had less to do with the distance and more to do with those bulbs are just dangerous and don't provide adequate uvb at any range. we've had this set up for 2 years and his vet is a full on reptile vet that has worked in zoos and stuff like that. i've never had a reason to not trust what he said and in our first visit with him, i talked to him about the advice i getting on here which is what saved sir henry at rescue time before we found the vet. he agreed with all that was said so that is the information i pass on to newcomers. we just have to drive almost 2 hours one way to see him.
the probe gun is highly inaccurate depending on what it is reading off of, but i am pretty sure that has been addressed with you. if i am remembering incorrectly, let me know and we'll get you hooked up with the "pros". and remember, surface temp has absolutely nothing to do with uvb levels. sir henry has a separate basking light and piece of decor directly behind his uvb and grape vine. there is space that has both, but he moves back and forth between the two most of the time and ignores that overlap area.