Hi Jim,
I am almost finished building mine. 6 sheets of 6mm ply and very little timber. The timber list that comes with the plans is totally wrong, sizes and amount needed.
So I have a lot of left over timber. Note to the designer to have a look at the cutting list that you send out with the plans for the Spindrift 12 cat rig to ensure that it is correct. Don't bother asking the designer any questions, as I have asked questions on 6 or 7 occasions by email with absolutely zero reply over the last 6 months. Pretty slack if you ask me. Having built 5 boats in the past these plans are by far the worst I have seen, but the boat is turning out great. Every designer should study from James Wharram as to how to draw up plans so that they are easily understood and accurate as well. Hope this helps.
Max