Mares Plana Avante Tre (FF). Highly rated and capable fins for freediving to 60 feet or less. Strong suits are thrust and easy kicking combined with superb maneuverability around rocks, reefs and for setting up hole shots. They will accept the Mercury weight set which requires a couple holes be drilled.
Sometimes, I still use the Sporasub long fins. I bought them from Biller about ten years ago. I had been using long fins since 1982, my first set being Cressi rubber types. I haven't kept up with the technology of long fins and there has been a lot of development going on. I know that most of them are too stiff, too awkward (SCUBA) or just fall apart. Somewhere out there is probably a really superior long fin but I don't have the facts, sorry. I do know that, a couple years ago, a Variant (?) fin received about the lowest score I've ever seen from Scubalab.