I would go farther myself with the UV. I would actually measure it rather rely on a manufacturers advise. UV is very odd, the reflectors can change it, the fixture it self, where it is. All can have an effect, it can be dangerous if you have too much and very unhealthy if you have too little. The current belief is that UVi can be used index meters are cheap and easy to buy. There are even little cards available. A max of 8-10 UVI is likely perfect it should fall off to 1-3 UVI or so.

If you cover the ceiling with a sheet of aluminum you can increase the UV up to 20% and a matte dark colour can reduce it about the same.