What do you think this cutout was for? (and what size screws for outwales)


Enthusiastic about Wooden Canoes
This cutout is on the port side of the canoe right up next to the front seat. Very neatly done. My grandfather did have a 3 horse Evinrude from the immediate post war period. My brother was wondering if was for the mount but I thought it a funny location. Also, what size are the screws that hold on the outwale? I wanted to replace them with new.

My first thought is diamond-head bolts (if this is an Old Town or Carleton) but if only on one side, that wouldn't be the case. Diamond-head bolts would be used for the seats and thwarts and would be on both sides. Maybe someone used them to secure something else (not a factory-thing)?
Should have been more specific. 1927 Old Town CR.The spots for the diamond head bolts are where the bow seat connects. It gives you a reference for the location of the cut out. The angle of the cutout perfectly lines up and matches the bevel on the ribs.