Hi Gordon, I used 1/2" plywood. The bowing doesn't really effect much except the end forms. Side-to-side bowing on the other forms won't make the boat unfair or measurably smaller. I had a problem with my stern form; I ended up freeing it from the strongback and holding it into alignment with an external frame (it's the tringle an the far left of the picture). I kept an eye on things pretty carefully as the strips went on; which is a good idea anyway. Next time I would use better plywood on my end forms.

- Chip
http://www.nwlink.com/~chips