How the heck are danskos supposed to fit? The 37 I tried on slips at the heal but I could not put a finger or pencil behind my heal. It is a sung fit and my toes almost hit the front of the shoe. The 38's are very loose and the heal slips when I walk too. I could fit a pencil behind my heal in them. They are overall loose nothing sung about them. How should they fit?Thanks!