I ended up doing the 6 hour off road race at Vultures Knob in Wooster. Weather was great (cold but clear), trails were dry and in great shape. Got a good 5.5 hours in on the single speed. Race started at 12 midnight Saturday and I got off the bike at 4:30am Sunday morning. With the time change it was 5.5 hours. Only stopped for new bottles and to switch light battery (did I mention it was dark and around 30 degrees the whole time).
Did 6 laps at 7 miles per lap, so 42 miles. I was feeling good, no cramps or other issues and could have done 1 or 2 more laps, but I did not want to overdo it. With the 34x18 gear and rolling terrain, did lots of leg tension stuff. Legs feel great today.