Roadwarrior,
We kept a high tempo at the beginning which, I think, shed the weaker riders. By the time we got to the first turn (at the bottom of a down hill, sharp right-hand turn) it was mostly more experienced riders, although there was at least one guy who was pretty erratic in his bike handling.
I haven't been using my heart rate monitor recently and didn't use it for the race. I pretty much know what my thresholds are anyway and how much I can push it.
Yeah, it was a lot of fun. Of course, since I finished pretty well in my category they'll probably put me in with the 4's (roughly equivalent to a real Cat 5) for the next race.
If that happens, I'll try to avoid getting my nose into the wind for very long. I also need to be more assertive in holding on to my position for the last mile or so up to the finish. The other thing I need to work on is doing some hill interval repeats so I can crest the one major hill (about 150ft in 1/4 mile) without burning too many candles.