Just removed my old bronze jib tracks and will replace them with Schaeffer racing tracks at 4" centers. They are mounted on the toerail, but the 1/4-20 FH mounting screws are THREADED into the toerail and a bent washer/nut is used as a backer. Slick, strong and no leaks in 40 years. Someone had their thinking cap on! Also, the first foot or so of the tracks are straight on both ends. Like steam bending wood, the ends are impossible to bend in situ. With longer bolts, the old track might even make a nice backer plate, full length. Nah, on second thought......