Thanks for the replies so far. I too noticed that the scraps of plywood that I have seem to flex more and are heavier than similar pieces of pine I got lying around in the garage. But my scraps were not exactly the same so I sort of extrapolated the feel I got from holding each of them and trying to bend them by hand. The plywood being only 1/2 of itself or so in the stiffest direction explains it - I had not thought of that.

As for the stiffness, I agree I do not want a very stiff paddle. But, in taking in consideration that I want a lightweight layup, I expect that there will be plenty of flex anyway. I like some flex but I tend to err on the side of stiffer rather than too soft for when more power is needed or in rough/moving water.

Lastly, the reason for me to look for the stringer variation is that someone who has experience with doing both kinds of paddles has had better luck with the ones that had a stringer. The ones that did not have a stringer tended to brake under heavy use due to compression fractures (both had foam inside for shaping them). He used fiberglass with carbon strip reinforcement under it and laid that all over the foam core.

What I'm thinking of doing is creating a plank that has the outline of the GP as seen from the wide side, then glue to it two pieces that when seen from the side (as if holding the paddle with the edge towards me) will create the other dimension of the paddle. So it forms a + shape that should provide rigidity as well as the outline for the general shape. I think of placing 4 strips of carbon in each of the sides, wetting them with epoxy, then placing stiff square section foam blocks in each of the quadrants of the plus and clamping that down lightly. That would have the effect of compressing the excess epoxy out of the carbon cloth while simoultaneously achieving a 3-dimensional sandwitch on all sides of the stringer.

Once the epoxy cures, I will need to sand it down to shape the GP. Once this is done, all that's left is to put the outside sleeve (I'm thinking either carbon or carbon/keclar as I did with my last paddle repair), wet that, vaccum bag it to cure, light sanding + fill coat + more sanding + clear coat and I'm done.

I was not sure if this single outside layer of "medium weight" sleeve that comes to about 1/2 mm thickness per the specs combined with the "+" shaped wood stringer reinforced with carbon would be comparably stiff to a full WRC paddle or not. Any guesses? I suppose I need to make one and see if it needs more or less...