It has to do something, but what. 0 to 3/8's is standard. 0 for three under and 3/8's for split. I shoot split and have been tuning at even (0) and 1/8 and 2/8's and 4/8's. I did skip 3/8, but I thought I'd try something extreme. Can't get the up and down kick out of a bare shaft. Started out and got the impacts in the same spot, but the bare still kicked. I'm puzzled.