I use the Kirk MPA-1 which is the Manfrotto 234 with an integrated Kirk Arca Compatible head. It works just fine for my lenses up to my 400mm f/5.6L. However, I usually don't use the head cranked down solid, I always leave a little give when I am shooting. That is just my style.
When I carry the camera on the monopod, the camera is always resting on my shoulder and is not waving in the air supported by just the MPA-1...

