Thanks for the suggestions fellas, here's another thing to consider. Our 480 did it, the 480r we demoed did it, and a friends 470 was doing it. In winter wheat we were travelling about 3.5-4 mph with 36ft. hd, wheat was doing 75bus_ac. The 480 couldn't do much more b_c of power, the 480r could do 4.5 no prob but then the "strip" would show up. I'm not convinced the problem is with the concave or with wind, it just seems that as these machines get overloaded its a strip on the left hand side of the sieve that shows up first. If this problem could be figured out, then you could unleash some serious capacity.