Semroc Wac Corporal Build, Part 1, Fin Shape

Here's how Estes shaped the WAC Corporal fins in the 1960s.

The tapered sides are incorrect and the tips of the fins have sharp corners.

I doubt there were many available pictures and scale data available then.

This picture implies the fin taper shown above.

The Peter Always drawing shows the taper from the wide root edge to the thinned outside edge.

Note the fin corners are rounded off.

From the Semroc instructions, 

The fin taper matches the front view above.

The root edge profile shows the correct shape of the fin, the widest point at the center.