Not too sure about the UV.
@Randomblame runs the same uv and had some problems with hanging height (if i remember right): the UV and led needed to be at differned heights to get spread and intensity right.
Its very easy to go overboard with UV, easy to burn, and you can also get uneven matureness of the buds leading to staggered harvests due to the top buds getting much more uv than the bottom.
You can use it at the same height if you calculate the hanging height first.
My currently UVB reptile tube delivers about 150-180μW/cm² at 30cm distance. It covers a 60-70cm wide area because of the added reflector. I can easily use the LED's at this height too if I dimm them down to ~240w. I'll get my 40-50klx and did not have a single problem due to UV light, although I used it 12/12h for the last three weeks.
But I will replace the reptile tube soon with Agromax PureUV tubes from HTG. This tubes will deliver about 250-300μW/cm² at 18"/45cm(440 @1', 170μW/cm² @2') and I can use up to 300-350 LED watt and still get around 40-50klx at canopy level but with twice as much UV.
I started in the last week of growth with 2 + 2h at the beginning and at the end of the day and continued to increase it until I arrived in the 7th bloom week at 12h. Not a single UV damage!
When I look at the UV level in nature, I think 150μW was maybe a bit too low. On the other hand, I have to say that the first UV run was a complete success. Although I have no lab comparison, I have grown the same cuttings with and without UV and with is noticeably better!
This are normal UVB levels over a day, up-to 450μW/cm² for ~3h. You could evaluate how many μW there are in total per day (like DLI) and tune your UV-lights accordingly. I think, 250μW for 3+3h indoors should work very well. Maybe I need to split that further into 4x 1,5h or 6x 1h. Let's see!
What I find even more remarkable is that the plants somehow looked healthier. They were also slightly more compact and more stable probably due to the high proportion of blue light. After all, it was 40w and such tubes have about 7000°k in CRI90, so plenty of blue.
If it's so worthwhile that even I, the old hand, use it, that must mean something...
I can only say, try it out! It makes a noticeable difference that you can not achieve with a few UVA LEDs. I had 385 and 420nm LEDs on my test light and even though an effect is also visible here, it is not so noticeable like true UVB!
PS. Do not forget to use sunglasses or even better, switch the UVB light completely off when you work in your garden. At over 40" there is not much UVB left, but you should nevertheless not look into the light!
