Estes Saturn V Fin Fix, Part 1

I'm doing a build of the Estes reissued Saturn V kit for a client.
Here's a fin reinforcement I wish I'd done on my first build of the Saturn V with the vacuform fins.

The hollow, vacuform fins are the weak point in the Estes Saturn V kit.
You cut them from the sheet and sand the overhanging edges to about half the thickness of the plastic. Glue both sides together and sand off the glued ridge, right?
These fins aren't strong and prone to splitting with a hard landing.
If you've built this Saturn V, it's not you! These fins don't have a enough edge to glue down the seams.

The leading and outside edges aren't too much of a problem, the wider trailing and root edges are the most likely to split open.
I did reinforce the trailing edge but didn't do any extra work on the root edge. That will be inside the fairing and epoxied to the main body.
(The instructions say to use plastic glue of the root edges of the fin. Trust me, use epoxy!)

In the lower half of the picture is the sanded trailing edge. I'd be afraid to sand any more off without going through the thin plastic. This wavy trailing edge won't look good on the finished model.

Above the fin is some extra plastic cut from the edges of the fin sheet.
This wedge shaped piece will be glued over the uneven trailing edge.

To make the piece, trace around the fin on the leftover scrap plastic.
Trace wide around the trailing edge, the excess will be sanded off after the glue dries.