The ballast is pretty much non heat-emitting, but I'm in an unheated large space and it's winter, so it doesn't signify much. I have plenty of air exchange but no chance for using CO2; leaky ancient stone structure, lol.
I always thought reflective material should be as close as possible? In any case, that's more winterizing than anything else, and provisionally put up to boot. By mid-January, I'll be redirecting the exhaust from the light fan back up under that insulation to heat the air around the plants. Gotta get my res off the ground too! Here's a larger view. I have radiator pipes overhead that complicate where i put this and hang that:
I do zero veg style frequently. These are mothers grown from seed, so once they are out of the way, I will have a smaller run of the same plants from clone, and then after that, depending on schedule and my tendency to jump strains, I'll do a couple of zero veg ops, while some other thing is vegging into motherhood.
I think it's a horse apiece in terms of yield; ten large plants will yield about the same as 40 small plants. (well, that's what I'ma bout to investigate, anyhow. I just finished a 40 plant sog in the same setup).
And everyone has one right? Don't want to be the newbe stepping on toes. After all these years its like an instant thing to me, and of course I'm certainly right always, except when I'm wrong. lol. What jumped out at me was your ballast hanghing inside the grow, if you have the cord length I'd move it out. They can add ten degrees. The reflective walls to tight to reflect may help to give some room. You have ventilation and or cO2? Just my pot wheels spinning, great looking grow. I wonder if you have ever used the same set up but skipped the vegging phase. suspect yield would be close but time much shorter.