Originally posted by kaseki I was firstly concerned about distortion of the camera frame such that the focus was no longer uniform over the focal plane, and secondly concerned about the distortion becoming permanent (metal distorted past its yield point). There will, of course, always be distortion in reaction to a load. If distortion is only a minuscule fraction of the depth of field and recoverable when the weight is removed then there is no problem.
Anyway, thanks alex645 for pointing me in this direction, and johnha for relieving part of my concern.
I have no doubt that Pentax engineers took this all into consideration when designing that lens. However,
depending on usage and age, everything will fatigue and in some cases recover, bend, or break. Breaking of course is an extreme that in this scenario would only happen upon severe impact.
Permanent distortion due to metal bending in the lens mount, I believe, would not occur unless there was repeated and prolonged abuse, undue force, and impacts. IF you think you will be subjecting this set up to that possibility, and no bracket currently exists, there are a growing number of 3D makeries that are beginning to make single rather complicated metal pieces. The school where I teach has this technology and the potential for solutions like this one are real.
Summary: Should you worry? Yes, if the camera is mounted onto a helicopter or off-road vehicle, etc. No, if you're using the camera and lens for "normal" studio or field photography with no intention of bricking it.
Note: I'm a photographer; not an engineer.