Don - are you talking about the very stiff, black US Divers fins with the 3 flow through slots? Yes, old school, still got mine from Army scuba training. Way, too stiff. The fins I use are the cheapo foot pocket type that the Y provides. I check to see that there are no cracks just forward of the foot pocket from wear because if they are cracked there you lose quite a bit of thrust.
I have some of the long, slender fins you are talking about and they are way too stiff as well. You want a fast, small kick that doesn't toast your legs.
For purposes of swim drills I use fins called Zoomers for my skill drills, and the foot pocket type for the hypoxic swims.