I have been running a 12 row since 2000, I don't think you need the corn seive, I never thought they cleaned as good as the regular seive. Have you change to all foward bars in the rotarIJ Or better yet put in a CDF rotar, it is amazing the difference in capacity, getting a cleaner sample, and savings in fuel. I think I used 10-15% less fuel both in corn and wheat. As far as corn head goes, the adjustable deck plant are really nice expecially like in my case I cut both a lot of dry land corn and irrigated corn. I also like having lateral tilt on the combine if you cut over terraces or rough ground. Just my thoughts Kurt