Peter,
On my BRe, i managed to install eye bolts, for cow-hitching my spinni ratchet blocks, with studs and nuts under. Located very close by the midships cam cleats for the mizzen on the BRe, there is a cut away in the cockpit coaming, with a small flat section of deck.
I did this by lying inside the side lockers. With a helper to pass tools etc, this is not as bad as it sounds?
The underside access is manageable, imo.
I hope to be able to do similar with these cleat fastenings.
I'm not sure I would want to attach these cleats to the coamings using just screws?
As an Engineer I prefer bolts to screws! Big penny washers needed.
PS I'm 5'9" and about 85kg, but aged 60, so won't be doing this for very much longer!