This is the view from inside.

Once the platform was securely tacked into place, I cut an 8- or 9” circle of glass cloth and draped it over the platform (this is with the boat upside down, of course), and epoxied it. The black dots are my markers for cutting. With the platform touching the deck like this, it isn’t hard to make the glass lay down tight to the wood while bridging the open gaps on the front and rear.

When the epoxy sets up, the now-rigid fiberglass made a good form for filling the sidewalls with very thickened epoxy. I added ground up chimney scrapings to get the dark color; it’s just decorative filler, after all, not structural.

That’s about it. I used a tongue depressor to make the fillet radius at the bottom of the sidewalls. You want to be sure there’s enough room for the compass base to fit.

Right now, I’m putting one in the CLC West River 164, a.k.a. the Hybrid Boat From Hell. The foredeck doesn’t have the same deep cut as the Coho, so instead of having the platform touching the underside of the deck, I used two small wood blocks tacked with hot glue to space it about ¾” down. It would have taken a much bigger platform to do it the same way as the Coho (that is, touching the deck), and I wanted to keep it small if I could. The resulting sidewalls are quite a bit bigger, so I’ve laid in an undercoat of epoxy thickened with microballoons as well as wood flour. I’ll put a darker-colored topcoat on it to finish it out.