OK, only posting this as I finished and don't like having "draft" in my race listing. Everything was going swimmingly, even thought I was looking for a PR, when about 1.5 miles in my right calf started getting really tight. My calves are (coincidentally) my Achilles' heel, both of them, so I don't take any pain for granted and I knew if I didn't stop running what was coming (lots more pain and a week or two off running). So I started walking just before mile 2. I would have bagged it but my wife was walking somewhere behind me, so figured I would too. I was not a happy camper. It was a good decision, which is something I am not known to do well while running.