I've rigged several taipan masts and I have successfully sealed my mast by using foam, stryrofoam or polystyrene, and silicon.



Make a foam plug up and coat the flat surface with silicon. make up another plug and do same. Force one plug down the mast. This one has to be a really tight fit and hard to push in.



The next one is pushed in so the silcon sufaces meet and the silicon is compressed which forms the seal. One trick I learnt early on was to drill a small hole in second foam plug to allow air to escape while pushing it in. The hole is also sealed when the silicon compresses.

I also seal my masts from very top to just above the internal downhaul.

Works for me.