Congratulations! I just did my first fleche as well - somehow even though the distance was the same, I suffered a lot more from sleep deprivation than any of my 400ks.

I didn't see this thread originally or I would have chimed in: I bring a change of shorts for 600k rides (then I put the old shorts on over the new for extra padding). All else, I just bring extra lantiseptic or chamois butter.