Great thread. I understood that a springer had to be un-clamped because it was supposed to move to absorb the spring shock. If I can zero it by clamping life would be a lot easier.
You thought right - you can not zero a springer by clamping it! The clamp idea the OP posted is I think just a simple way of safely resting the rifle between shots - a bit like 10m target air rifles sometimes have a bipod attached even though they are shot standing.