I like your style, Tweed.

there's not much that can't be fixed with a drywall screw and a bit of enthusiasm imo.

I have decided what to do with the Martin.

I am going to drill a 5mm hole in the heel cap (slightly bodywards as Richard Bridge suggested above) and tap out the hole to M6.

into the hole there will be screwed a (30mm -40 mm?) length of M6 stainless steel studding which has been drilled through the center and tapped out to M4, and this will be filed flush to the Micarta heel cap.

a M4 bolt will be threaded into the insert and this bolt will secure the strap button.

overkill perhaps, but it will look like a professional installation.

if there turn out to be problems with the guitar tipping forward then at least the installation can be concealed by removing the cap, grinding off the end of the insert and fitting a new cap.

then I can go the Martin recommended route.