Estes Gyroc Build Part 4, Balsa Truing and Filling

Edit: Don't sand the root and outside edges even like I did! The flap (lower fin) is not as wide as the upper fin. Line up the outside edges and the root of the rear flap fin will be raised to clear the body tube so they can flip!
See this correction post HERE

After gang sanding the like parts the root and outside edges didn't match up. The fin set on the left is before sanding and evening up the sides.
On the right is the large fin pieces, taped together and after sanding.

The fin edges were sanded flat on a block with 220 grit sandpaper.

The fin stock is 1/16" thick. You don't see 1/16" thick fins on models anymore.
Some forum posts have talked about balsa warping when the applied CWF dries.
The balsa will warp down the grain lines when only one side of the fin is drying. When the other side is painted the drying filler counteracts the warp and the fin should end up flat.

Just to be sure, I set the fins in a heavy book when the filler is about half dried.
This is a side view of the root edge of the four wing pieces.
All are flat and straight.