Man, with a roundbar in the APS and a roundbar main concave, you've got the best combo there is for reduced fines.

One thing we noticed with our Lexion was very few tips broken off the ends of the kernels. it is the best grain quality we've ever seen.

I'd do my darndest to keep grain going to the rotors to a minimum.

I'd suspect that the few bars of concave you've identified are causing a few fines, but not a huge factor. They may be contributing, but not the main factor.

I'd side with the theme that it's a hybrid x year issue unless neighbors with the same hybrid and a different machine are having vastly different results.

Sorry I'm not more help, but I'd suggest looking at other factors before I built something or pulled a concave out to modify (a BIG JOB) and was disappointed in the results.

Luke