Bill,

Did you look at the link in the above post? It would appear that in context the 5% refers to the mast chord as a portion of the total chord of the airfoil (mast + sail) and that he is planning to build a typical teardrop shaped mast with a cord of roughly 5% of the sailplan.

It does not appear that he is asking about building a teardrop shaped mast with a cross-section equal to only 5% the chord of the mast as you imply.