If I could manage, I think a layer of glass on the inside and some lightweight filler would be my preferred method. Might be a bit tricky as you would have to do it in two operations, first do the glass, then glue the glass in position and add the filler. I would hate to add weight and glass to a carbon Tornado mast!
Sad to hear that your Marstrøm Tornado mast leaks due to what sounds like a poor solution. This is something the technical comitte of the ITA should adress.