Hi
For what it is worth.
I just checked a piece of replacement Gunwale stock I had trimmed. And found it to be 3/4 X 3/4 ash. Routed half round on the outside edge. This was an almost exact replacement for an older Mad River Explorer in Roylex. The original gunwales were not 1/2 round on the one side. The gunwale stock I used was provided by the dealer I do a bit of repair work for.
I realize you might be able to use the lighter thinner stock, but I thought knowing what a manufacturer uses would be useful information. Particularly should you be thinking about hooking up a motor to the canoe.

Have fun with your project,
John VB