Centuri Flutter-By Build, Part 8, Fin Gluing & Masking?

I wanted to mark the back of the root edge to line it up with the rear of the interior body tube.
The right side of the picture shows the first attempt.
Because the fins are two different shapes they can be hard to line up.

The inset picture shows the second try, this time I got it right.
The fin position on the body tube is critical, the model could wobble if it isn't right.

Be ready, with only half of a root edge to glue on, the lower fins won't want to stay on the tube.
Here's how everything lines up.
With the lower fins are glued to the interior tube it looks like the root edge fits both body tubes.
The upper two fins don't touch the interior tube, there is a gap!
The original Centuri design had all four fins against the stepped body tubes.

The instructions show a shorter launch lug. The supplied lug is as long as the root edge of the fin.

The instructions say nothing about masking.
I slipped a short scrap length of BT-50 over the interior coupler, you don't want paint on the green coupler!
You could use masking tape but this is just simpler.

Both halves were separated and got a white undercoat.