On my 98-ft. of Rohn 45, I have a 3-stack of 204BA, with the lower two fixed
(30 and 65 feet), and a 1022 Ring Rotor at 83 feet, about 6 inches above the
top set of guys, holding a Hy Gain Explorer 3-el. 40m yagi. The placement was
in part for the reasons K4OJ mentioned, allowing the guys to take up some of
the stress from the ring rotor turning, and in part to have it midway between
the two upper 20 meter beams to minimize interaction (though I found terrible
detuning when the 20-meter beams are perpendicular to the 40m beam. The 204BA
booms tend to be self-resonant on 40 meters!).
There's a bit of an art to climbing around a ring rotor, but any way you look
at it it's a pain. I use two or more lanyards on my climbing harness, and
carabiners, so I am always 100 percent connected to the tower. I have thought
about putting a couple of steps of angle iron to make the climb-around easier,
but haven't been doing enough tower work to make it worth the trouble.
I find climbing around this Ring Rotor much easier than the larger one I've
worked with on Rohn 65 at W3PP.