For one of my kids rigs we used a cut down sail. Couldnt find a suitable mast anywhere. I was building a bamboo trellis for my dragon fruit. Found a suitable length n diameter piece of bamboo. Slid it into a 40mm piece of md electrical conduit. Ended up same diameter as rdm. But bcoz of internal thickness i had to use sdm extension. Dropped mast into the extension n it sits on pin. Ended up being great bend curve for the sail. Nice n light and it floats. Super easy for the kids to uphaul. In lightwinds it easily keeps up with a properly rigged sail.