I have not done this exact thing, but I have used epoxy to glue down skin on the cockpit base ring. No need to slit the skin and epoxy under the skin. The epoxy easily penetrates and attaches Dacron (polyester) by just painting on top of the skin. That way the skin will not be distorted due to the stretched tension before you glue. That will cause lots of issues.
I would suggest you widen the contact area of the skin by adding short additional stringers in contact with the keel. I also suggest you do something to harden the slot, precured glass potted into a wider slot, for the same comments as Bill Hamm gave you . Wear/ jamming of sand or dirt.