It is very common to use high rise mounts in Pistol Silhouette competition higher than what is on Ted's rifle in that picture Google Ken Light manufacturing scope mounts. The advantage with a pistol is moving your 2 hands apart for better stabilized hold rifle scopes are then used. I have one of his 3 or 4" rise mounts for my Thompson Contender. I used to have a 5 or 6" high rise for a rear grip XP-100.
Mike