CZ Shadow line and S2 are the best canidates for a single action modification. They do not have the firing pin block safety so you get the shorter reset of the trigger to feel more like a 1911. I have 4 CZs, most being polymer models, P07, P09, SP01 Phantom but my SP01 Shadow is the smoothest. All have Cajun Gun Works or CZ Custom trigger/spring upgrades and polished parts. The first shot double action is so smooth you really don't even feel them.