"z" wrote in message I'm kind of in the same
boat, re a friend's house, but the problem is
ensuring the existing box is sufficiently solidly anchored to hold up
the fan, without ripping apart the ceiling. Which has just been
painted, of course.

had a similar install problem. went ahead and opened the ceiling to
a 1 ft access 'circle'. Was able to provide secure anchoring for the
light fixture box. Hung fan using a circular trim plate with
decorative molding to cover the hole. Shop for the trim
cover plate before cutting ceiling hole.

lee h