Aha, I've been waiting for a build like this since I have 4 similar 10watt LEDs kicking around (cool white I think) that I ordered as samples to try out. Haven't done anything with them except hook a 9 volt battery to each to make sure they work. I'm assuming they're the same form factor as the 100 watt ones Reefie links to in his post? Would they look something like this?
Sounds like your friend has used aluminum channel to mount them with only a couple of fans? This is my plan as well. So no optics at all? I ordered mine with glass optics and some sort of plastic bracket the optic fits on to. If you end up having success without optics, that's a bonus. Also got a couple of heatsink/fan integrated gizmos that one of these 10 watters could be mounted directly on to. Might be more useful for the higher wattage arrays like 30 & above.
I'll be watching your progress with keen interest. I have seen threads on various forums that dismiss these 10 watt arrays as not having sufficient penetrating power, but going by your par readings, they may be talking through their hats. Some hobbyists have been beating the Cree drum for quite a while & it's nice to see positive results from something other than discrete 3 watt Crees or comparable Bridgelux etc.
The huge advantage I see in using these 10 watt LED arrays, is that the operating voltage is typically between 9 & 12 volts DC, so you could theoretically run them off a standard battery bank charged by solar, wind or whatever. Wouldn't need drivers or power supplies to convert AC to DC and dimming is possible with a simple variable resistor. Although for peace of mind, a current or voltage regulator to limit those paramaters if something goes awry would be a good thing. Definitely interested in more details of how your friend has constructed the fixture!