What Matt said , most of us old farts had one on our bows , before carbon , to get more speed , but the negitives far outweighed the benifits for most of us , and noone I know is useing one anymore . I used to shoot 25" 2213s out of a 70 lb mathews with a 28" draw .

The farther away from the pivot point of the grip you get the more critical / less forgiveing your bow becomes .