When I put a 843 on a N6, I removed some of the flighting on the right side of the cross auger to prevent over feeding the left side. In the gap in the middle I mounted rubber flaps to help feed in the fluff. It worked fine.
We put an 853 on a N 5 had to add fliting to the left side take out some fingers and then we narrowed the feederhouse openning to keep trash from rapping on chains make sure you exstend the striper bar to the end of your covers. This made big defferance in ground speed.