I agree, the best way to find out is sign up in a cat 5 race and see what happens.

I remember years ago when I first entered college I road with some hard core guys and could keep the pace line. I entered my first cat 5 race got my head handed to me. But, it gave me a race under my belt, and I got serious and learned to train to race. I joined a team and went on to do some hard core racing. Most importand was learning to train the right way. Learning to peak when I wanted to do specific races. Since I never made it to Europe I guess I didn't learn it well. But I had a blast along the way and still race some today.

You may want to get a book called Cyclist Training Bible by Joe Friel. It's a great source of information for someone considering racing, or just improving training skills. It's avialable at many LBS or large book retailers.

Good Luck!