Interesting how this topic keeps resurfacing. Since I contributed to this thread almost a year ago, I've given up on my Force Fins and gone back to JetFins (with steel spring straps), and I'm glad I did. The bottom line: these are still the fins I want if I have if I have to work up-current, and particularly if there is any kind of trouble and I need to get somewhere fast. But I know these are not for everyone.
I now think that what makes a fin work depends a lot on individual physiology, including both musculature as well bone structure and angles. I've also noticed that people who have a background in competitive swimming and/or water polo (in their youth) often tend to like very stiff fins, though I haven't got enough samples to make this a rule yet.
I'm keeping the Force Fins, but only for use as "macro" fins on muck dives. They are sometimes easier to keep high and clear in very silty locations than the Jet Fins.
I frog kick a lot, which is another reason I'm giving up on the Force Fins, which really don't work well with the scissoring/feathering frog kick I like to use, which might be something like the one fdog uses.
I have a pair of Master Frogs I still use once in a while. I loved them when they were new, but found that they lost stiffness after a few hundred dives, or maybe it was the travelling. I like stiff fins, and unfortunately my Master Frogs started out nice and stiff, but they aren't now. Not only that, but the lug molded onto the fin for attaching the strap is also breaking off on one side. I know I put a lot of miles on my fins, but still......
One thing about Jet Fins, you can't do much to them just by using them or packing them in a dive bag. With stainless steel spring heels, these fins are basically indestructable.
Frogfish...