OK, the numbers are in:
400W station closest: 22oz
400w station behind: 24oz
Both trimmed and dried. The station furthest had the benefit of reflecting light from two walls, as well as overlapping light from the LED station next to it (and of course ambient light from the HPS in the rest of the room).
So that's 1.5-1.7gpw. These stations average about the same with the 600HPS lamps, with 20-24oz being typical.
Bottom line: 400W LED = 600W HPS
Next trial will be the same, but with one plant per station instead of two, as was the original design. New plants are in already and will take another 7-8 weeks. This is a 7, maximum 8 week strain.