Thanks, Ex, I appreciate the advice and encouragement. The suggestion to train for the length of the climbs is a good one; I'll work on that. I'm not bad riding in close quarters, especially if I trust the other riders--but that's not the case in a cat 5 race.
You're probably right about Offthebackistan, though I hope to avoid DFL. I'm not really looking for results, but rather for the experience and fun.