The sleeping bag zip miwaks bodysuit maker found for me unfortunately proved unreliable when I stress tested it with the actual tail. I spent time last year hunting down YKK continuous zip tape & fittings to custom a length, which involved carefully removing teeth from the tape. Then I removed the tail sheath, whip stitched down the end caps seam allowance, and centred the new zip to the inside. Next steps are to machine sew down & resheath the tail.