Steve,
I've used this monopod.
http://www.manfrotto.com/neotec-mono...th-safety-lock
This one is David's (cooldry) and has come in handy holding the 200-400 and the 600 that I have.
I also have a few Gitzo carbon fiber tripods too. They all work. Whenever you have glass over 200mm I think it's always a good idea to use a mono or tripod.