Today it depends very much on the course sailed as to which "spinnaker" cat will "win" races. If races are set as windward and returns without reaches then the most tactical and importand legs are the "runs" and with spinnaker but no centre boards you will suffer no disadvantage, all depends on the ability of the skipper and/or crew to pick the correct angles and side of the course. Although you will obviously suffer some what on the beats, from watching the F18's race for a few years now, any advantages on the beats will be lost in seconds if that best beating boat doesn't get it together on the run, so just "go for it and exploit your "good points" and you may be in for a pleasant surprise.If you sail an "olympic" style course ie trianglr loop triangle, then there are the extra reaching legs that you have no disadvantage on, and dont let any one tell you that a "heavy" can't beat a boat that is ultra light. if the skipper and crew use their weight on the boat in the right way, weight can be a great advantage in all sorts of weather, not just the heavy.
Darryl