I've got the
Viparspectra xs1500 pro in an 80cm x 80cm tent. I'm 4 weeks into flower, on full beans (100%) set at 12inches up it's burnt the tops of the collar's in the center. I don't have a par meter, I was running on a lot of the manufactures saying you want to be hitting 1000ppm. Thinking I need to be at that spec has sizzled a few tops. Now,
Dr. MJ Coco at Cocoforcannabis, his website says 700ppm is ideal and with my limited experience I think he's probably right 700-800ppm. This leads me to believe that the xs1500 pro would flower 90cm x 90cm perfectly or maybe even 1meter x 1 meter if it's on 100% at 14''-15'' (38cm) off the canopy. I'm back at 75% for the last 4 days and the collar's on the side of the tent still look happy as Larry.