The coupler is cut in two. You'll only use 1/2 of the coupler in the build.
The fins were gang sanded to be sure they were all the same size.
This is all three of the upper fins on a sanding block.
The Wac Corporal fins are slightly rounded on the outside corners.
I rounded all three fin corners at one time for consistency.
Be careful, it's easy to take too much off - I did.
Here's six lower and upper stage fins after shaping and rounding.