I just checked a freshened up unit I have on hand and confirmed that the slug is free to move. I didn't take it apart and check it from the inside to verify it's open all the way through, I just checked it from the outside.
Excellent Work!
Will you be storing the car for winter? If so I think it's a good idea to depressurize the unit by keying off and gently pumping it down with 20 or so pedal pumps. That way it's at 0 pressure during storage.