I think Quique flew the OS 1.40FI when he did because it had significantly more power than the 1.40L's that were commonplace back then. That was right when he started flying the Smaragd, and they were draggy airplanes, I don't think 1.40L's did nearly the same job hauling those airplanes around as the OS's did.

Granted, YS did come out with a stronger motor, but back then, that was the stronger of the options.