Thanks Rolf -

Interesting thoughts. The 5.5u page at www.performancecat.com says that it has the same hulls as the sloop, so I'd be surprised if that was a problem. But it could be that the shrouds where the forestays are anchored are at a different position on the hulls, and as mentioned above the 5.5u has a taller mast. So even if one could take the 5.5sl jib and attach it to the 5.5u, I would need custom forestays.

The mainsail on the 5.5u is actually a newer mainsail. It seems in excellent condition, and in all honesty I can't complain about the boat being slow. It even tacks pretty well (although all I have for comparison is my old sunfish and a bunch of rental hobies and prindles).

The spinnaker would be nice - but it is an expensive addition (might as well get a new boat!). Also, I want to try sailing downwind when my mainsail traveller is fixed. It should be a bit easier.