Maybe I'm doing something wrong,,Ive gone through four heads ,,all medium crown,,and within a couple of weeks,,they stretch and hit the neck cut where it meets the body,,and Im not getting them nowhere near up to A tightness,,Ive never had this problem before,,Ive tried the Remo,,and the Snuffy Smith heads,,all do the same,,anyone else have this problem,,and is it possible to use a low crown on a flathead banjo?