Manta, mantaind.com , has excellent spring straps in 2 different models to fit most any type of fin.
I found the Turtles to be too flexible and rudderlike, but they do have a very large foot pocket. I only wear size 9-1/2 or 10 shoes (size 10 DUI) so a pair of AquaLung Super Rockets did the trick for me.
I also have a pair of XL Cressi Rondines (also with spring straps, had to modify the attachement point some) that fit wonderfully. Not enough propulsion for diving with doubles, but fantastic for rec diving with a single tank, and very comfortable.
theskull
I found the Turtles to be too flexible and rudderlike, but they do have a very large foot pocket. I only wear size 9-1/2 or 10 shoes (size 10 DUI) so a pair of AquaLung Super Rockets did the trick for me.
I also have a pair of XL Cressi Rondines (also with spring straps, had to modify the attachement point some) that fit wonderfully. Not enough propulsion for diving with doubles, but fantastic for rec diving with a single tank, and very comfortable.
theskull