I'm in the contrary opinion it seems.

For me personally, I wouldn't do the 100 miler. I don't doubt you already are or would be soon, aerobically fit enough. Not at all.

Rather, I'd be more worried about such a big increase in distance and what it will do to your joints, etc. Before I did my first century some years ago, I suffered problems with injuries due to rapid increases in distance. My cardiovascular system said GO, but my joints weren't nearly as cooperative. If you are a runner then you probably already know the 10% rule as far as increasing weekly mileage.

Do what feels best, but definitely, listen to your body very closely. Whether you do the event or not, best of luck