Update: my PF has improved to where I don't notice it any more, even after dance class. Just in time to go back to Scotland! I really like Birkenstock insoles, even more than Superfeet; they are absolutely going with me this time. Other than proper arch support, what helped me the most, I believe, were the excercises you do standing on a step, where you dip your heels below the step level and then lift them above, keeping the balls of your feet on the step.