Steve, you make a good point. The more I think about it, it's questionable what difference the jib would make upwind - the uni is already a very fast boat. If I had to stab a guess, the crew weight (~360 lbs) and the fact that my fiancee likes to sit smack in the middle of the tramp despite my efforts to balance the weight onto a single hull, have a lot more to do with speed than any lack of sail area!

Tacking/turning is remarkably easy with the 5.5u, at least in comparison to the hobie 14 and my sunfish.

Where did you find the boomless spinnaker? If you see it again, do let me know! It sounds like it would be faster to rig, and perhaps easier to use also?