I deformed my old Scubapro Jet Sport fins in exactly the way you describe, but I got them to regain their shape just by laying them flat on the floor and putting my gear bag on top. My new, thicker Hollis F1 LT fins didn't quite fit my weird foot bones at first, but I was able to soften them up in some boiling water and reshape the pocket by shoving a sneaker in sideways. Good luck!
