The Second variant of the Hartford made a number of improvements over the S-15A. This aircraft was the intended production model. The most notable improvement was speed, which was gained by adding props with greater surface area. Visually the Smith company elongated the nose and windscreen, as well as shortened the wings. A new pattern was programmed into the wingtip strobes, and improved avionics were standardized. The aircraft was never advertised with a standard internal configuration. Customers could choose freight, pax, and combo configurations during order placement, or accept a base-model fuselage with intent to have private maintenance departments personalize the aircraft at the customer’s home facility. As a result, the feature model was not fitted with extra windows or cargo doors.