Has anyone tried a Vortex (Venom or Viper) on the new PDP 4". I received the Vortex plate from Walther and am deciding which of the two Vortex to buy. The gun will be used for self defense (likely less than 25 yards), and I'm not sure whether to get a 3 or 6 MOA and which Vortex model? Any suggestions? Thanks!