Commander Aero or First Flight in Dayton has the STC.
Re: the big winglets and strakes, TCAC analyzed them and they could help in certain regimes but, as noted, about the last thing a Commander needs is more effective wing. Iíve had a -10 840 to FL390 and even tested a -5 840 at gross with high time engines to find a 1.5 degree deck angle at FL310. Thereís a reason you donít see VGís, hub caps, strakes, and other aero fixes on Commanders. They simply donít need them.