I was so thrilled with how comfy my VFF sprints were, I went out an bough a pair of classics. Unfortunately, I found the heel tab intolerable, no matter how loose the bungee was. The only way to avoid the Achilles-stabbing was to flex my ankle the whole time, which was not only annoying, but also prevented me from that mid/forefoot strike I'd come to love. So, it had to go! I wanted the classics for casual wear, and kept the sprints for running. So, disabling the bungee wasn't an issue.
In case anyone else runs into this problem, I detailed the mod:
See following replies for the rest! (too much for 1 post!)