Estes Black Star Voyager Build, Part 13, The Lower Fins, Steps F

I had to sand a steeper angle on the inside of the Q pieces so they would fit together .

Notice the sanded bevel is wide enough and ends at the tip of the Y piece.

This shows a good fit of the center Q pieces.

Here's the interior of the assembly.

I tried for a overall better fit, but there is a slight gap inside towards the top of the Q pieces joint. This won't be seen on the finished model.