After taping big pieces of cardboard together to make a fullsize
mockup of the spec concrete footing (3 1/2 foot tall pyramid), I can
see it'd be quite an impressive mass that would do all the things you
have all mentioned. Thanks. And be a huge job. So now I'm looking
at using a guy wire to the top of the post to provide the resistance
to being pulled in (as volleyball nets and other applications do),
instead of that giant buried hunk of concrete. (I also printed out a
number of US patents for alternatives to buried footings for sports
nets. Some interesting ideas these people have had.) By modifying an
Oz-Post spike (a nice system for putting up fences and decks without
digging footing holes; I did a 600 foot wood fence with these a few
years ago), I might even be able to do this whole job with minimal, if
any, actual digging. The weight of the tennis post itself and half
the net is pretty small, less than 50 pounds, though if I use a guy
wire, that will end up pulling down on the post as well, adding to the
apparent "weight" needing to be supported. The angle of the guy wire
(its length to some kind of stake) determines this. The longer, the
less downpull, but I don't need people tripping over guy wires in my
yard. I'm mocking this up as well to see if guy wires can be lived
with.