The best place for the pivot point where the arrow contacts the shelf is directly over the deepest part of the grip. If i were you I would do one of two things unless you want to try some sort of rest. My first inclination would be to glue a small piece of wood, perhaps from a wood shaft, directly over the deepest part of the grip....or, I would take a rasp and reshape the shelf so that it is crowned with the highest point of the crown over the deepest part of the grip. Back in the day when that bow was made most every one used an elevated rest so that the shelf, as it is on your bow, was not an issue since the arrow, presuamble, was never going to make contact with it.