Having an earth conductor won't change the thermal efficiency of the driver. Meanwell drivers are pretty robust and you'd need to have quite a warm ambient temperature coupled with high load to overwhelm its passive cooling. Whether or not its heat will effect the QB is tough to know without some ta...

You should have plenty of light with approx 90,000 lumens over a 4x4 canopy.

You would most likely get a little more than the rated current out of the constant voltage 'A' version also. This is true for both of mine.

Maybe go 90cri 3000k instead of the 3500k for that extra red. Run them all off the one driver with a switch and the remaining 4000k's make a great vege light. I also use a 4x4 and started with 6 cobs but modified the light to have 8 and now 9 cobs. Seems to give a better spread. This will obviously ...

You may as well run the 'C' cobs - given that they will be close to maxing the driver out and can be dimmed if necessary. MY only concern would be if the heatsinks could handle that almost 100watts. The other option would be to add more 'B' cobs or even more 'D' cobs to create a better spread. I wou...

Can EB2 strips be run without heatsinks below 700ma? Or did I just think I read that somewhere...

Will you build three separate fixtures for each driver and set of 5 cobs?

And how will your existing light fit into it all? In the middle? Or at the end? If it has a different spectrum its worth considering.

Just series them all up if they need to be run at 1400.

Paralleling the 304's would split the current (but not double the voltage).

Personally I would run a small 12v driver for the fans.

Paralleling up those CPU fans in a high voltage CC circuit is asking for trouble.

Guessing you'd want the circulation fans on constantly too? Two drivers make this easier.

Are you in a 3x3?
2 foot Samsung or Bridgelux strips might also be worth thinking about.

Otherwise - 3000/3500K 90CRI Vero29 SE's are super cheap on DigiKey right now.

Seems too close for comfort for me. 3590's are maybe worth it for the efficacy at lower currents you're looking for? Could always get an A type driver and dim ever so slightly so that your vF for the 4 Veros fits the driver as well. You're already slightly over 50w/sq ft so you've got plenty of light.