I built a 20 ft pokeamoke back when clc was starting up. Its a round bottom kayak and has speed like no other kayak I have built. It was a difficult build but was worth it, It was a fast double and I am rebuilding it as a single. I am also building the sail rig to go on it. I also built the Jimmy skiff and a 18 ft chesapeake and have deceided to use the sprit sail from my skiff to power my pokeamoke. It has a keelson and thus a good stout place for the maststep to mount. My Question is what would be the best guess for the measurment for mast placement? . This is my first post. I have not built in a while but am back now! Thanks much!