I agree to the 14' 11" length, definitely go with 3/16" strips, and I too am building from the book with my own offsets. I didn't even cut the recessed forms beforehand, for the reason that they weren't listed. I also didn't cut the taper the strongback on the the ends, just fastened the third forms in from the ends to the end of the beam.

I may be doing it all wrong, and it's not without some issues, but I'm having a great time! I'm even exploring lashing the strips on with monofilament line, and running two courses of strips at a time! You can see some details on my blog: http://www.driftingson.com A big new update will be coming soon, with about half the hull stripped, including a report on the how the use of the lashing technique is working.