Another poster said that the 4010 3 PH (which is probably identical to the 2210's) floats in the middle position. I found that it does indeed float there. Just lower it a little bit, get off and see if you can easily lift the arms. I could on mine.
If it's like the 4010, you can push the rockshaft all the way to the "up" position and it'll automatically return to the middle. Not so with going down. I suspect it'll float either somewhere in the "down" area or middle position but haven't actually tried it with the lever left in a down position. The manual says to return it to the middle position. It doesn't say where it floats.
On the 4010, I think you can lower it to a fixed spot in the down area and bring it back to the middle and the implement will stay where you lowered it to. Therefore, you can mark where to go to with a marker to run your cutter, for instance. In the case of a plow on the back, you'd lower it to the ground and it'll float up over any raised spot but won't drop lower. If you left it down, it won't exert any down force but would then float down if the plow dropped into a low spot. I'm not sure whether it would then float back up once it levelled off or ran into a hump.
I'd try it with nothing attached, rockshaft all the way down and with rockshaft in the middle. See if you can lift the arms. Just lower the arms a little bit first.
By the way, what are the min/max lift heights at the ends of the arms on a 2210? Asked a friend who has one, and he didn't know.
Ralph