John -- just wanted to say welcome to the group, my boat isn't rigged for spinnaker either right now but one thing you have going for you is the plate at the mast step -- you should be able to clip your turning blocks to it instead of having to drill spots for them on the deck.
Does your racing club not have a jib and main or cruising class? I personally would be more interested in going to a 135/145 genoa than worrying about the spinnaker for now. If you are racing, you will probably want the 155 unless you have 10-12 knot plus breezes all the time. But a smaller one would be more fun and easier to sail with normally.?
Tell us about yourself, what do you plan to do with the boat?
