Possible alternative...
I've considered adding a spinnaker, but the cost keeps me from making the leap. I don't think I would be able to get the value back out of it when I trade up. Just the sail was pretty expensive. I did however add a whisker pole to my 18.5 for this season and that added to the power a fair bit. I don't race, just cruise, but it was a nice addition that can be handled much easier short-handed.
