I've recently switched from DiveR composite fins in an Omer foot pocket to the 300 foot pockets from C4 using the C4 Indian soft (25) blade. They are amazing. Easily a pound lighter than anything I've ever worn and extremely hydrodynamic and efficient.
As far as coral concerns/worries from freedive fins, our area (Destin, Fl) doesn't have coral beds, just sand bottoms and wrecks.
Cheers