I think the most difficult part of building your own led light is figuring out the spacing of the led's,cobs,or whatever. All the led's i've looked at have a very narrow beam. Even when advertised as having a 130 degree spread, a look at the datasheet will show you how fast the lumens drop off anywhere not directly under the led.
I wish the datasheet's would give the spread from a given distance, maybe some do but i haven't come across one. This is even more important if you are working with a limited height in your given space. Some of these high powered cobs will bleach the shit out of a plant if they are kept too close. Now you are in the position of wasting power burning a hole in your garden when you should have gone with a spread of lower powered leds.
Looks like you have a good setup there Jimmy, maybe if i can stop thinking about things too much i could actually get something like that going.