Stretch stretch stretch. Don't take your lack of PF for granted. I was told (professonally) that your/mine problen is (probably) due to tightness in the hams, calves and achilles tendon. And high arches (can't do anything about that). Stretch before and after. Never had it until I was 30. Doc said you get tighter with age. I blew off streching for 16 years. STRETCH!!!!!!!!!! Later had motron cortizone and orthotics. Was still to dumb to religiously stretch. Now I have bone spurs. I do wonder if the thick soles lead to foot instability. I never had problems with my $8 marathons(now asics)