I did, apologies for the typo.
Cobs seriously need that much distance though? That's insane! LEDs sure have come a long way. I've been wanting a COB to play around with for a while, but I could never justify it. It'd take me a while to see savings, as I'd need quite a few COBs to replace my 1000w DE no?
Regardless, I rarely do indoors anymore so I suppose its a moot point. But I'm interested in the knowledge regardless!
I imagine COBs are like HID lights, the issue is hardly with the heat itself but the light intensity. It's theoretically possible to have enough cooling in your grow, combined with a vented hood to nullify any heat related consequences. However, the intensity of the light itself on the plants is what will cause problems.
In fact, not many people know this but too much light can actually inhibit photosynthesis as it literally causes cell death. This makes sense when you consider the sun's cycle and how it moves, outdoor plants never get direct sunlight for the full amount of time the sun is out as the sun is only overhead for a few hours out of the daylight.
I've actually practiced dimming my lights to mimic this. The last 4 hours of lights on, I'll dim my light down to 600w. Then, when lights come on again it's still at 600w. I change the light back to the full 1000w for 4-6 hours (depending on veg or flower) and then dim it back to 600w for the last few hours of the day. I've experienced no downsides, and some strains have actually given me better results.
Back to LEDs though, I remember when they first came out that CO2 supplementation wasn't viable due to the lack of intensity from the LEDs. But if LEDs are truly as intense as you say, and the need for higher humidity due to VPD then wouldn't supplementing with CO2 provide COB users with better results?
I know absolutely nothing of LEDs, but reading your post the first thing I thought of was adding extra CO2 to the mix.