Sounds like an interesting project. Recording the weights, distance dropped from, etc. could take some doing.

The tension is easy to come by with out pulling the kayak from end to end. Tension will result to the inside layer when a force is encountered from the outside inward. The beam strength in cantilever is most influenced by the webbing of the Ibeam (moment of inertia) and top and bottom pieces to resist twisting, in the kayak, the strips thickness is the webbing and the fiberglass is the top and bottom of the Ibeam. In canilever, seems to me the first thing to fail would be the cedar in compression at the lever support point then with some loss of the ibeam thickness the inside piece fails under tension.

I would make the test piece way over size and then cut parts from it for testing this would ensure the same epoxy mix and application to all test parts. Have fun and let us know what you find out. Throw in some of that tuff 1708 stuff too.