The shear bar adjustment is set where you want it. I usually set it pretty tight with new knives and shear bar and move it wider as the shear bar rounds off. Knob controls how much knocking before the shear bar motors reverse.

I would remove the pan under the feedroll. That is there to catch corn cobs, I think grass could wrap and cause a problem. We have never left it in for hay, we always change it when we change heads.

The hydraulic knob under the left side panel goes one way for hay and the other for corn, I don't recall offhand which way is which. I am pretty sure that if you leave it on the corn setting, your hay head float won't work. I know that if you leave it on the setting for the hay head, it won't lift the corn head. One of the knobs on the console is to set how much pressure the hay head has on the ground, another sets lower height limit.

A 900 should be a beast. Care to share how many hours it has and what the current market value was?

If you need to ask questions, I could give you mine and some other phone numbers of folks that have been running these for 10+ years. Drop me an email if you want, contact info is in my profile.