Heavy duty tripod advice...

Most wildlife photographers lean towards the 500/4 over the 400/2.8. I've never used the 400, but I've heard that it is not as hand-holdable as the 500 (although, with the series II lenses, I don't know if that is still true). I bought the 500, but I don't do motorsports and have no experience with them. I would think a combination of the 70-200/2.8 with 2x and the 500 would cover most bases. Another strong contender might be the Sigma 120-300/2.8 with 2X. This was just re-worked and looks like a very nice piece of glass.

The new 400 is supposed to be as easy to handle as the old 500, I have no idea how easy that is!

In the UK we're quite lucky the wildlife can't kill you, maybe the 400 will have an advantage over the 500! I don't know.

You can also look at the Custom Bracket gimbal head http://www.custombrack​ets.com …bal-series/cb-gimbal.html and if you use the code at the end of this article you can save 10%
http://www.studebakerb​irds.com/purchase.html

I use it on a Feisol 3442T tripod and it is rock-solid steady.

nellyle wrote in post #16052286
The new 400 is supposed to be as easy to handle as the old 500, I have no idea how easy that is!

In the UK we're quite lucky the wildlife can't kill you, maybe the 400 will have an advantage over the 500! I don't know.

Just my 2p!
I used to use a 400 F2.8 L but quickly moved to a 600 F4 L IS, after a few years I sold the 600 as I picked up a reasonably priced 800 F5.6 L IS - I think yo can guess my opinions on focal lengths! The 800 can be a little long but only very rarely in my experience, though I do carry a 300 F2.8 L IS as well if I am not walking too far.

As to support I have tried a number of tripods and heads and have settled on the Gizo 3530LS systematic (now superseded) and a Wimberley 2 head. Even with the 800mm I don't feel the need for a 5 series Gitzo tripod having compared them side by side. The Wimberley is very expensive (bought mine secondhand) but is the best I have tried (and I have tried a few) so far. This is not to say others will not do a good job though. I also use a LensMaster RH1 for my 300 F2.8 and whilst it is no Wimberley it does the job at a quarter of the price! The RH2 would probably be better for a 500mm though and it is still very cheap!

Remember that when seeking Mr Rouse's advice on focal lengths that he is more adept at getting closer to his subjects than most of us mere mortals!

As for that Markins part, though I am intrigued by the idea, I don't believe the claim.

What it is doing is turning the ball head into a pan and tilt head.

No one has ever claimed a pan and tilt to be the equivalent of a gimbal. The weight distribution and balance are totally different.