Also, and apologies if this sounds a bit dumb, does one use a monopod like this directly attached to the lens, or with a gimbal head attached? At football matches they seem to use them directly attached.
At football matches the action all happens in one plane, so there's very little need to tilt the lens ap and down. With birds that's not the case.
When I got my new Gitzo monopod (after realising that handheld video just wasn't an option) I tried several solutions for use with my 7D and 300 f2.8 lens.
First I bought a Manfrotto 234RC tilt head and replaced the QR clamp with an Arca-Swiss type. That meant I could use the the plates already attached to my gear (my other heads all have Arca-Swiss type clamps). But the 234 head isn't designed for something so heavy. Even fully tightened there was a lot of drooping - and I mean a lot. I also like to carry the monopod/lens combo over my shoulder, but that was impossible as the head slowly tilted under the strain. So the 234RC got put away.
I thought of using a gimbal head - but that was so heavy it made it really difficult to use and carry around. I tried a ballhead, but that was too wobbly.
Then I tried just attaching the clamp to the monopod. That worked well except for when I wanted to get birds in flight or high in trees. I ended up lifting the whole assembly - which doesn't make for good stability. I also like to carry my gear over my shoulder, with the monopod at 90º to keep it out of the way. Impossible with this setup.
Finally, I bit the bullet and decided to spend some money on the problem. I bought a
Really Right Stuff High Capacity Monopod Head. I couldn't find a UK dealer so I had to buy direct. And it wasn't cheap. But I reckon it was worth it. It will easily hold my gear at any angle, so unwanted droop is a thing of the past. It's very light which is important when walking around with it all day. And it's small, so it fits nicely in my monopd bag.
The attached images show my 20D, 300 f2.8 and 2x TC attached to the RRS head (which is attached to my Acratech Ballhead - the RRS head has an Arca-Swiss fitting on its base). As you can see, it easily holds it at any angle.
Overall the whole thing cost me around £250 including shipping and VAT. That's 10 times as much as the 234RC but I think it's worth it to have something that actually works.