I'm not sure how 18th-century planemakers attached horns to planes, but I decided on a sliding dovetail for strength.
Thinking it would protect the fragile corners of the dovetail, I added shoulders so that it would sit back from the front of the plane by way of a shallow recess.
The dovetail is hidden because the horn covers the joinery. I have no idea if this matches the method used 300 years ago, but it worked really well.
Even though there is a cross-grain situation with the horn and plane body, I glued it in place. We'll see what happens over time.
I had thought to circumvent any cross-grain issues by burying the bottom of the horn in the body and cutting a deeper mortise than necessary to allow for movement. Changed my mind for whatever reason, but I do think that's a viable option.
The last two photos show the horn with oil applied. It also shows the decorative border I carved along the lower portion of the plane and the final shape of the plane's body.
I should have glamour shots of Sven ready on Thursday. The oil is drying, then I'll apply some wax to the outside surfaces.