Thanks for the good vibes!
The light I have is an integrated hood/ballast setup that was designed for 3 x 3 spaces. The PPFD does drop off around the edges but at 24 inches and 18 hours the DLI is still about 35 even at the edge of the tent. I keep the light at 24 inches pretty much the whole cycle. I have experimented with running it as close as 15 inches, yields went up a bit, but the overall quality was not as good. As far as I can tell, at least for my setup, I get the best balance of quality and yield at between 40-50 DLI. Whenever I have pushed it higher with the CMH and the plants start to show light and heat stress.
I think there are three reasons they are so stout. The first is genetic, the second is higher DLI from sprout (40-45), and the last is the 4200k bulb. It has a lot more blue and less red light than the 3k bulb, which keep the plants nice and compact.