The remaining airframes were stripped of their rocket modifications and "74-2065" returned to regular airlift duties. "74-1686", however, retained its other Operation Credible Sport STOL modifications and was sent to Robins Air Force Base, Georgia. There, in July 1981, it was designated YMC-130H as the test bed for the MC-130 Combat Talon II's development, under the project name "Credible Sport II". Phase I was conducted between 24 August – 11 November 1981, to test minor modifications to improve aerodynamics, satisfy Combat Talon II prototype requirements on STOL performance, handling characteristics, and avionics, and to establish safety margins.