If you have the knife in the forward setting take the first wear plate off and turn it around so the bolt hole offset is less in front. This will give the knife more front to back travel.
Spring loaded holded downs work realy well also, keeps the knife section down on the guards which helps to slice not chop through the stems better. Yes they are more mantaince but they pay for them selves very quickly with better feeding and less losses out the front. Rolf