If you must shoot from the bench, keep your body as up-right as possible. Firstly, if at a public range, commandeer all the sandbags around you. Secondly, set up the rifle on the sandbags so that you can shoot in the up-right position with your left hand holding on to your fore-end. It may seem to be a bit unsteady sitting that high but it will help as far as absorbing recoil and not get head-aches.