I used to do a bunch of that kind of thing, now it's just more fun to ride the Harley  The closest I even came to twin rows (which I always liked the looks of) was 15" corn. Never got it to do better than my 30's, so kinda gave that up.

First off I really disagree w/ the posts that knock you for the population change. One thing there is that I think the individual hybred 'can' be the limiting factor moreso than population. if it's a good big, flex ear type, you're going to see little variation in yield until you get WAY on the extremes of population.

I once did a plot using the hydraulic drive on my planter to check pop:yield & used one of the old (now) beer can hybrids (Garst 8481) = not much flex at all. It had to have high pops to yield, or so we thought. Ran pops down to 17K & up to 60K, with only a couple in between. True, the 34K came out on top, like we'd have thought, but the 17K & the 60K yields were almost identical & NOT that far off from the highs!

If you do another plot like this one again, I would look for hybreds that respond to the higher populations, if for standibility concerns, if no other. I'd look for the same charactaritsics if I were doing a 15" row plot. & then compare those results to what I ran in a normal 30" hybred. 8481 stood @ 60K, some of the big, tall flex ear types would have gone down in June @ those pops!

One of the ideas of narrow row/twin row IS to run higher pops than 'normal' w/out crowding the in-row spacing. If you don't give the twins the advantage that you're looking for, there was no point doing it. I can see doing a check w/ the 30's in the higher pops, but I wouldn't either sweat it or throw the results out the window.

I still think it's cool you're doing it & sharing!!