I tend to use the monopod mostly for telephoto shots. In the past, I tried mounting a ball head on the pod, but was never comfortable with the set up, especially for vertical shots. So, I've switched to using a tripod ring instead. And I have to tell you, I am so much happier.
I use the Canon Tripod Mount Ring A II (W) for my 70-200mm f/4L zoom (often with the 1.4X extender). First of all, the tripod ring is much lighter than an equivalent ball head. The camera is definitely more balanced on the monopod. And I don't have to buy an additional quick release because the ring serves that purpose. And the added bonus... no quick release plates to fool with.
The joy gets even better while shooting. I absolutely *hate* trying to shoot vertical shots with a ball head. The slot is never in the right place, and I feel like the camera is about as unbalanced as it could possibly be. But with the tripod ring, I just loosen the knob a half turn, rotate the balanced camera to any angle I want, and tighten slightly. It is wonderful.
Once you use a tripod mount ring for your telephoto, you will never go back.