The range owner doesn't want the SAs he rents to be dry-fired. I could / should indeed insert dummy caps, and plan to do so at my next session.
Great idea, the video thing. Will try to figure something out.
Eye dominance is definitely THE thing IMHO.
I'm right eye dominant, but cannot manage to close my left eye so I'm sort of forced to keep both open. I do turn my head to the left, in order to decrease the influence of the left eye.