I'll sometimes make a groove for a half round to strengthen a seam.

Dry test fit.

Added trunk and sides to the hatch.

I often overlay the reference and the model to check fit. Notice the error at the bottom of the window. I added a little frosted tape with hatch marks for a measurement..

A second view of the model and a reference photo confirms the error. See the frosted tape with the pencil marks (middle of trunk)?

I call this the ugly part of modeling. I use Elmer's White Wood Filler.

Sanded with a black nail file board from the dollar store.

Added some Evergreen #240 half round for the window gasket.

Teenie-weenie miter pieces for the gasket radius.

The three pieces fit into place.

The driprail and that's about it.