Right on, man. One thing I want to mention is the setup I'm showing you is a solder free setup. The COB's are poke-in and the thermal pads are easy to apply, no thermal paste involved. Simply purchase 1/8'' aluminum angle bar and use M3 screws to mount the heatsinks to the frame.
Not sure how good you are with a drill but all you'd need to do is drill the holes in the frame to screw in the COB's.
I'm more of a DIY type person who will always DIY if I can do it myself. Some people don't have time for all that rigmarole and there's nothing wrong with purchasing something that's all ready to do. I've heard only positive things about Timber row Lights.
On a side note, have you considered a Quantum Board from HLG?
https://horticulturelightinggroup.com/collections/lamps/products/hlg-550
That is a 515W light and it would be great for a 4x4. Double that up and you'd kill it in a 4x8 room.
I've got more experience with QB's than COB's which is why I bring it up.