I've done three 1200Ks, all on geared bikes. Times were 63:24, 79:10, and 87:15. The clock runs the whole time. The first route I was trying to ride fast, and it was easy -- it only had 18,000 feet of climbing on it and the weather was good. The second I was taking it easy, it was a tougher route, and it rained pretty much the whole time. The third was very difficult (somewhere around 50,000 feet of climbing), it was blazing hot, and I was taking it easy. I had between 9 and 15 hours of sleep on each of these rides. More on this kind of riding here.

I'll try wider tires before messing with the bars. I don't think the bars themselves create road chatter so much as tranismit it. And I'll see how the position is as I increase the ride length -- I'm riding 200K tomorrow on the fixie on a hillier route. More data collection!