I haven't done that race, nor do I have any advice about it. That's great that you were able to do the 54 and felt so good afterward, tho!
I will tell you, though, if you feel like you want to do the century- DO IT!!

I'm always of the athletic mindset that if you want to do something just get out there and do it. I signed up for my first Iron distance triathlon before I had even done a sprint tri. People thought I was nuts and that there was no way I could do it- but I did!
There *IS* a big difference in how the body feels at around 60-70 miles and how the body feels at around 90 miles, that's for sure! And there's definitely a HUGE difference in how you feel after 54 and how you feel after 100.
I would ride long one last time before the event (next weekend?) and see how you feel. If you can ride about 75 miles next weekend and feel good, then go for it! However, if you feel like crap after 75, then I wouldn't do it. Then again... maybe I still would.
