I use that size ferrule and cut the stations (built up with bamboo cutoffs that are simply the ends of the strips flipped over and glue enamel side to enamel side so the apex faces up). I multiply the station by 4 and divide by pi. Or, is it somewhere in between, knocking off part of the corners, and making the four sides into eight sides, then just filling the gaps between the 8 flats and the ferrule with epoxy? Where do you get your quad ferrules? I looked at all the suppliers listed on the Rodmaker's web site, but didn't see any advertised as being for quads, except at one site that offered ferrules with either six slots or four. Or do you make special ferrules with the end of the ferrule round, and the rest square? If so, how far into the ferrule does the bamboo go - clear to the end (male ferrule), or just to the place where it turns from square to round? When you put a ferrule on a quad, do you cut away the corners of the quad so it becomes circular with the diameter of the flats, or do you add 4 slivers of bamboo to build up the flats to the same diameter as the corners? The first method would seem to me to cause a weak spot, while the latter would seem to make the ferrule much larger than really necessary. (Subject may have been on the list, but I didn't see it if it was.). And realized I haven't seen anything on the list about putting ferrules on quad rods.