Its funny I just rode an MS 150. I actually just rode 1 day due to the weather. We had the option of 75 or 100 miles. I did the 100 mile ride. I live in the mtns and my ride was flat. So I really had a lot of confidence. I had only rode 66 miles as my longest ride so far so when I got to that mark I was very aware I was riding further than before, I had no problem even at a brisk pace for me. I think the main thing is setting your own pace. Dont get with a faster group than what you want to ride. To me I really dont go by the 10% rule or anything I am sure they are good guide lines. Even me at 42 and 255 lbs I have in my mind that I can do the ride and its going to be my pace. Ocassionally I will get with a faster group but then I will slow back down. One thing as with the MS 150 there are plenty of stops. I think its all in the mind. Like a guy told me once. The body can last longer than the mind. I would suggest that you dont rely that much on books and articles but just keep riding and maybe do a couple longer rides before you do the century perhaps a metric.

Just my opinion.

Steve