Originally Posted by
Stagecoach
Manfred,
Mount fixings (screws) is the term I should have used for the engineers reading. For the non engineers, the point of weakness being the holding screws of the metal parts into plastic.
For a non supported load extending forward the affect of vibration caused by the mirror is going to be greater than that if that load is supported. This can very easily be seen if using live view and simply lightly touching the lens, without support it will spring, with support it will spring far less or not at all. By rig, I was referring to camera/lens with respect to the tripod movement.
This of course would not be a problem if it were possible to use mirror up, but very often it's not.