I think Todd made a good point when he mentioned that the Northern boats are more likely to attend a southern event when it is in the middle of the winter and not so close to our season. In my mind, a midwinters means January or February. For the F18 class in particular, we also have Tradewinds labeled as our Midwinters, and SF was the Southern Area Champs, so those took a slightly higher priority on the schedule.

Also, nothing at all against HCA, but calling the event "Hobie MWE" might hurt F18 turnout because when folks scan a calendar they may not realize the regatta is open to non-Hobies. The class did try:
http://usf18.com/hobie-midwinters-is-open-to-f18s-save-the-date/