Aircraft Spruce has some headset jack housings. But they were rather pricey (~$25 each). Malcolm told me about some housings he made, so I took some wood, shaped it, covered it with fiberglass, painted and then applied some release agent.

Then I covered it about 4 layers of BID with some Triax around the edges.  Repeat four times and I’ve got $100 worth of headset jack housings.

To install, I cut four holes in the keel, located the position of the screws, then installed nutplates for mounting.