Hi there.

What seems to work even better for me is to wear an old pair of sports sandals that I trimmed to fit into the footwell (otherwise they were just too big!) I think it is because the heel strap then carries the weight of my legs rather than all the pressure being focused on the 'corner' of my heel that makes the difference; it's more like a pair of real shoes with a heel cup that spreads the pressure around.

Pete,
TDY in Spokane