Ian,
Thanks for the map.
I once met a great nephew (or something like that) of Mac, who claimed to have heard via family legend that Mac never thought the routing was that good, because he was forced to use the old plantation home as clubhouse. While I can't confirm that one (and he never showed me any written proof) I don't think of it as a great routing. Really, the really great natural holes are 4, 6, 10, 11, (although, both have semi-blind tee shots now where you can't see the green) 12, 13, and maybe 16. Poor natural holes at places like 14, etc. The rest are average by my criteria.
It is hard to route a course where there are predominant broad slopes down from a corner of the property. Obviously, about half the holes have to be uphill. The really good ones I list above nicely cross existing valleys, rather than descend or climb hills.