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Hi,
the sucker slide bars are for very light paper, as for the biting, I don’t think there is any way to adjust the pressure of the grip, its one pressure for all. hope that helps,
Re John

If you have a dent in the stock you must have a foreign body in the gripper or some damage to the inner rubberised surface . I would as a quick fix put a strip of sticking plaster along the rubber face to act as a cushion . you have to replace it regularly though , and it gets you out of trouble. Have never had a set re conned myself but you used to be able to get component parts but god knows where today.
you could look at the two knuckles on the gripper setting and check they have identical settings and the adjuster to pull againt the gripper springs is the long screw that runs across the top of the face of the hub it is noticeable by the long spring through which it runs .This long screw will alter the pressure on both grippers at once . any variation from gripper to gripper is dealt with by the connecting link T1314 this link makes adjustment on the individual gripper but moves on /off in half turns usually only severe wear will need taking up on them. they are usually the setting for opening the gripper but you can do no harm having a fiddle and patience will see you put it right if you get it wrong , do remember to mark one gripper as you easily lose track of which one you were moving .