Why a "Sidekick"

[chauncey]

I am upgrading my support system to a Dutch Hill P900 tripod with a Markins M-20.

I'm wondering about adding a "sidekick" type device.

The glass involved would be 70-200 f/2.8 ISL and 300 f/2.8 ISL mounted on a Ds MkII.

Tell me I'm incorrect when I suggest that adding a device like this simply adds to the likelyhood of increased vibration by adding a piece of equipment and raising the center gravity away from the ballhead.

When would you'll use something like this?

[blonde]

don't worry about vibration from the Sidekick. as for when to use it, i would use it all the time with the 300 2.8. it is a bit of over kill for the 70-200 but when you are talking about the big guns, the sidekick really makes life much easier.

[CyberDyneSystems]

On the right ballhead, (like your M20) a Sidekick is great for the larger lenses!

As to why, because it's about 5 times faster easier and more stable to use than a large lens mounted directly to a ballhead.
I'd not worry about vibration, both the 300mm and 70-200mm you have will help to damp anything using IS as well.