Or, maybe, since you are trying to sight-in an optical sight, do what the big bore rifle shooters do. They shoot standing up, with the forearm resting on a padded surface, and their off shoulder steadied agaisnt a pole or other guide to reduce sway. In this way, the recoil just pushes them back, and they do not have their upper body weight resisting the force. Since it is highly unlikely you will have the bench and bags in the field, the zero you get from sighting-in standing will be far more representative of the results you will get from a hunting shot anyway. You get to win twice. Better zero, and less punishment.
One a practical shotgun course, I had to sight in a Mossy 500 in 2 3/4 using slugs from the prone, on fine gravel, and I had let my partner take my elbow pads off the range. Makes one focus on his shots, to ensure a good zero in a minimum number of rounds!!