We run grain front position for front and grain rear for rear no matter what crop as long as you have shock kits installed. Some guys have run rear in corn position after cutting top of block to allow same lift as in grain rear position. That may help prevent a plug when suddenly jamming a bunch of material in but could cause problems getting the feed started if running a crop with high amount of tailings returned for rethresh. In that case you could have alot of tailings resting inbetween the chains after running empty for a bit. I've found it very hard to get feed going over a bunch of tailings if chain isn't close enough to the floor. Good luck