For sail material - I had some extra tyvek house wrap that I used for my first sails. I just wanted something to setup the boat with and make a pattern. That type of tyvek is really too stiff - I think when I try to make some paneled sails that I will use rip stop since I can get that fairly cheap at the fabric shops. Once past the learning curve Ill probably try some mylar or Tri-Spi material that the racers are using. I am planning on using 1/4" double sided tape for the seams with no stitching.

No idea on the mast - mine is one piece. One thing I did was to make a multi-position mast step so that I can move mast position as needed to change the center of effort of the sails if I need to to get the boat to sail balanced in different winds. I would assume that the CE is good since your using plans for a working boat (looks like the step is fixed in the pic on the web site)
I was just worried that with mine I wouldnt know until it sailed. I will have some ability to rake the mast for CE adjustments but I liked the idea of a multi position mast step. My step is a simple rectangular ply mounted on the deck with multiple holes to receive the mast base. There are a bunch of different way to do it.

I guess I should figure out how to post pics - If I do Ill let you know.
spin