[Helios 1984]

I strongly suspect that, at least for a handheld shot, the camera lens mount can support more weight than you can. If you're trying to hold the camera with both hands on the camera body, rather than the lens, with a very long lens, it is going to be very difficult for you to hold. With even a 200mm lens, I doubt that you could hold it steady enough to get a decent shot at anything less than 1/1000 second.







For tripod mounted shots, as other have said, if the lens has a tripod mount, use it.







As for neckstraps, with the strap attached to the camera only, the camera will lay against your chest, with the lens pointing at your feet. This puts very little stress on the lens mount, so I wouldn't worry about it. It might be uncomfortable, but it isn't going to damage the lens or camera.







I made a shoulder sling for my camera. I got some one inch strapping material and a buckle for it. I cut to an appropriate length for my torso. I added a large (1 1/2 inch) key ring over the strap and slipped it through the strap lug on the camera. Now, I can carry the camera with the strap over my right shoulder and under my left arm. This allows the camera to ride under my left arm when not in use. This also offers it a little protection in the form of my left arm.







To use the camera, I reach back with my left arm and bring the camera to my eye. I learned, way back in the sixties, with my Spotmatic, to support the camera with my left hand under the camera, while my right hand stabilizes the camera and operates the controls. With a long, heavy lens, my left hand shifts forward so that it supports the lens.

I use a sling as well, I have the habit of holding the camera even when it is under my shoulder. When my heavy 200mm is mounted, I hold the lens while I'm walking.



note: I found this excellent article on how make the most of handhelds - https://www.pentaxforums.com/reviews/long-exposure-handhelds/steady-position-1.html