Only 38 watts? That's surprising, but assuming they are monos, I suppose you'll get a bit of a boost because of it. I've become accustomed to just using phosphor whites, but need to add more. I'm currently using 4x10W and it is not enough for 1sq.ft. IMHO. I have a 30W CW on the way and think that will bring up the energy level enough to give proper yield.
So if you can get 1g/W from that, I'll be most impressed. Even 0.5g/W would be commendable. In any event, I'll be very curious to see how this turns out. Keep the weekly updates coming.