I ran this loop yesterday. I was running pretty hard but not really red lining it because I was alone and didn't want to trip and hurt myself. I meant to announce it ahead of time on this forum but I only had Internet access on my iPhone and this forum wasn't really working with that. I'm claiming a time of 6:23:14. Here is my trip report: www.isaiahjanzen.com/2010/07/running-buchanan-pawnee-passes-loop.html
Some background since I am new to this forum. I ran the Presidential Range in New Hampshire in about 8 hours in September last year with my college cross country team. I also ran a double marathon "fun" run on Cape Cod on May 9th 2009 because a few of my college track team members and I wanted to see how far we could run. I am really more of a "short" distance specialist with a 10k PR of 32:58 and half marathon PR of 1:17:06 on a hilly course.