I've been curious about the DNZs, specifically for Tikkas. The top surface of the Tikka receiver is totally flat, and the DNZ (or any other top mount rings or rails) is only clamped down with tiny 6-48 screws providing tension. It seems to me it would be possible for the entire mount to slide slightly on the gun if it ever got bumped.Another vote for the DNZ one piece on my Tikka. My buddy likes his UM set