Sorry for the late reply to your question Gary. I went and found out some more information on mast sections from the catamaran expert up here in Brisbane.

The mast section with the internal ribs was made specifically for the Mari-cat class. The length of the mast for these boats would be to short for the Mossie and there are only a few left. But wait there's more. One longer section is still left that is long enough for a Mossie mast.

The supplier of this mast section owns the die to make these. A deal could be made to run more of this section if the association spoke with the supplier.

The supplier strongly suggested going with a larger section mast the same as the Nacra four five. more readily available and a more reasonably priced.

So in summary as it stands realistically the original Mossie section is out of date for a square top sail.
Dave 1724