depends of what readings of uvb you get ! for example i go for the 10.0 cose the mesh i used is thicker ! so the 5.0 for me was to low !
i'd say 10.0 is ok too depending of the mesh and how much it blocks the uvb,the height where you put the bulb,how large is the cage etc...
personally i find 10.0 better, and i know lots of pple who use 10.0 and nothing wrong happened!
Im useing the Arcadia T5 12% and my panther cham loves it! 1 of his favorite basking spots reads 108 on my solar meter. Thats still only about half of what can be reached in the shade outside on a sunny day
I used 10.0 for four years then have now switched to the arcadia T5 12% bulb. I always use higher than a 5.0 as they just don't give out enough for a 4 feet high cage. As said above the sun is alot higher than any uv tube and we all try and take our chams outside for uv. nothing bad will happen when using a bulb higher than 5.0