>yes, the original post was about handholding, which was why I was
>suggesting the longer lens would be less stable and more prone to
>shake. But yes, on a tripod, any long lens with tripod mount
>at the center of gravity will be more stable.

Hi--
But the point of my original post was that the longer lens has
the advantage in steadiness (at least until fatigue sets in),
which is true from my experience (mentioned in the original
post) in addition to being supported by physics. Even in the
worst case (a lens attached to a camera with the camera attached
to an insufficiently strong tripod), the longer, heavier lens
would be less affected by camera induced vibrations than a
shorter, lighter lens.
Hope this helps.
David Ruether