If you come to Okinawa, you won't need your dry suit. I dive a 3mm in the winter and a swim suit in the summer. We did get some 66F water on the Pacific side this winter when I wore my new 5mm.
My dive buddy stated the only reason he bought force fins so that he could use them with his dry suit. What you are saying seems contrary to what he said that one size fits all. So Force fins don't come with spring straps? My dive buddy also said that his force fins sucked for surface swimming. Is their something about having a complete swimming stroke that make them only suitable for underwater? I would rather spend my $400 going toward a new dry suit.
My buddy over there told me water temps are <60F right now??
ForceFins have the advantage of being easily and quickly resized down. They are not really a one size fits all solution, but as close to it as possible. Given that I have a size 13 foot, I wear a XXL with my drysuit boot, add a comfort instep and wear it with my wetsuit boots, I can get away without the instep, but I have a better fit with it. So in that they can be one size for all conditions, not one size fit all divers. My problem with demonstrating the Original for you is that I only have a pair of XL's and they are too small for my drysuit, they fit my wetsuit fine, so once you have wetsuit weather, I will try my best to make it out there, besides, I understand you have beautiful dives out there that I am looking forward to anyway.
As for Spring straps, ForceFins use a bungie setup, that is more comfortable, just as easy to use and they don't add extra weight and negative trim.
Surface Swimming is very easy in ForceFins, the trouble is not the fins for surface swimming the problem is technique. If you kick hard upwards (recovery) the fin will pop out of the water as with any fins, ForceFins tends to excaserbate this due to the reduced resistance of the recovery stroke. So the fix is quite easy, kick down, then relax your leg, your leg will unconsciencously be in the right place to kick. It sounds stupid but it works well and once you have mastered it you move as well on the surface as you do submerged. Most people find it easier to roll slightly to one side and kick if you really need to get somewhere.