Had some extra time and a new Sigma 150-600mm, so I took a trip to the Basel Zoo to give it a go.
One thing is very clear. A lens of this size need support. I used a tripod this time, but I can see that a monopod would be easier to use to some of the areas with more people around. I've already been looking into this and I think that I'll be going for one from Sirui.