So if you are using a T5HO single bulb linear fixture with a 5.0 or 6% bulb on top of a regular screen top you want to have the branches 8-9 measured inches below the fixture. This puts the chams body in an approximate 3 UVI level where they rise off the branch. You do not want it closer than that or you will put them into overexposure levels.
This would be the same for a vivosun quad fixture as well because the reflectors come down between the bulbs. These also produce a ton of heat so if you have a female you need to test temps because you do not want them hotter than 78-80 max on the highest basking branches. If the quad is doing it for temps you want to remove the basking fixture. Make sure with the quad that the position of the UVB bulb lines up with branches below it as well.