I have the lens in question, have had a 5D and have 1Ds3's. Even on a 1Ds3, I would not let the lens hang down and be thrust around, pulled by the camera's lens mount alone, at least not very much or often. In the case of the 5D2, this "goes triple." As a previous poster said, the metal mount on the 5D is screwed into a polycarbonate mirror box. Why this matters is that putting the strain of the high weight of the 70-200 f/2.8 IS II on the mount, with the multiplying factor of foot-pounds of torque around the fulcrum of the mount, transfers all that force to the weakest links in the chain - the connection to the mirror box, the mirror box itself and the connection of the mirror box to the rest of the camera. Somewhere along that chain, something will eventual bend, move or distort and the result, if not some obvious separation, will be the much more likely small movement of the lens' optical path out-of-parallel with the plane of the sensor, causing either total or partial misfocus, or both. The tolerances aligning the lens with the sensor are mind bogglingly tight and they all depend on the alignment of the lens mount to the sesnor.
To summarize, it is better to be safe than sorry. If you must carry the lens and camera together with the camera strap supporting both, try to hold on to the lens with one hand, to support most of its weight, as much as is practical and possible. Otherwise, carry the lens in a camera bag separately and only put it on when you are ready to shoot. Otherwise, you might like to build, or find and buy, a strap system for the lens, not the camera, and carry the combination by the strap to the lens; this would lessen the strain on the camera mount to an easily tolerable level, as the camera weighs much less than the lens.
Regards,
David
--
Keep learning; share knowledge; think seriously about outcomes; seek wisdom.
