I’m finding that about 120 watts a panel ( meanwell 240 powering 2 boards) at two feet from the canopy is the max for flowering in my setup. I was getting foxtails in week 6 of flower and backed them down to 100 watts a panel to finish out the run.
I vegged this crop under 120 watts a panel but they’re mounted solid to the ceiling, no yo-yo’s, so basically the 4 feet
@shambler mentioned would work for me in veg at 120 a panel. I’d never get away with 6 inches from the canopy at that wattage though, I usually screen them to keep most of the canopy at 2 feet. I do get some buds that get closer, so maybe a foot away in spots in my setup. You have to watch those tall buds though, they can get light bleached real easy.