we don't have our corn head on any more but i'll throw this at you,they like to have the corn head run at a 20 degree angle for standing corn and at a 23 deg. angle for down corn,and that measurement is based off of the stripper plates,so the row unit mounting tube should be on the same plane as the row units.  in addition do you think that possibly your are too low with your bottom beam? in other words how does your auger bed match up with with your feeder house floor?