My advice to deal with pf is to forget about the shoes and work out what's happening in your calves. Sometimes the problem is caused by tight calves, but because the sole of the foot can be weaker that's the bit that gives way. Make sure you do plenty of calf stretches, especially after wearing heels, driving or walking up hills. Massage is good - and a professional sports massage person can quickly identify whether you have any knots going on that might be causing the problem. If you can have a look at the Trigger Point Therapy Workbook by Clair Davies, that explains a lot. I had pf for ages, but now I know how to deal with the warning signs a bit of stretching and work on the calves sorts it out.