To be honest with you, I don't know. I have zero experience with using LEDs to grow. The practice was just starting to take off when I took a "little" break from the forum a few years back, and I've only recently returned. So my questions are more for my own education - and curiosity - than anything else, lol.
With that being said, my gut instinct would be that 8" from the canopy is awfully close. I've had plants grow right up to the bulbs in grows that used (both types of) fluorescent bulbs. And I've seen them happily "bumping" against the glass with moderate-wattage (400- & 430-watt) HPS air-cooled fixtures. But I have been under the impression that
some (IDK which, it's just a general impression at this point) LED panels are pretty intense... and the one time I decided that if a lot of watts is great then even more wouldn't be a disaster at all (lofl) and tried growing with a 1,500-watt HPS, I saw light-bleaching in my plants (also heat damage, high utility bills, etc. :rolleyes3 ).
With LED panels that had the small individual LEDs, which were a few different wavelengths, I've thought that a certain height might be called for - regardless of the intensity levels - in order to more fully blend the spectra into a more uniform and even sort of illumination (as opposed to having spots of individual colors hitting different leaves, lol). But, again, this is just something that I've assumed, since I have never had the opportunity to actually try an LED panel. And with the type of product that you offer, that doesn't seem like it would be a factor?
I'm happier consuming sativas and sativa-leaning hybrids, and to grow such critters, one needs a good bit of light - and intensity of same - as most of them originated somewhere between the Tropic of Cancer and the Tropic of Capricorn where the sunlight energy is much more intense than in the more northern (and more southern) latitudes. So I might be the kind of person who tried running an LED panel
a little closer than average 
. Got to feed the monsters so that they can return the favor later, ya know, lol.
I've wondered whether or not many people actually hang their LEDs
too high and try to wring too much coverage out of their lights - but I've often wondered the same thing about HIDs (see above comments about sativas). I have also wondered if, perhaps, the coverage estimates by the various manufacturers/sellers (regardless of the type of lighting) might be just a tiny bit optimistic. But I realize that this will, of course vary depending on the circumstances such as the strain(s) being grown, the size of the grow room, the reflectivity of its walls, whether or not a light-mover is being used, and whether the grower is using one light source or multiple ones (in which case there can be a bit of a "third light effect" between two of them).
I really don't know much at all about growing with LED lighting, I guess - and what I do know, I have only absorbed via reading instead of using them myself. Maybe one day I'll get rich (or at least a little less poor
) and be able to see for myself how well they perform... and whether someone who has grown with many types/wattages of lights but never LEDs can easily learn to use them.
Err... My apologies for rambling in your thread. I don't
start out intending to write novellas.
-20~40°C)
