Hi,
I've owned a 5.5 Uni and two 5.5SL's. They are excellent boats. As Mark said, you'll need the spreader bar to distribute the loads for the stock sloop jib.
However, I was wondering if anyone has messed around with a pole-less spinnaker? I sailed a Dart 6000 that had a small wire bridle attached to the bows and the cutest little spinnaker that launched and doused from a bag on the trampoline. It was great. This is what I want to do for my present boat. The jib is inefficient upwind and too small for downwind. I believe that even a 120 square foot spinnaker without a pole would dramaticlally improve offwind performance. I made a spinnaker for a Stilletto 30 from Tyvec - got 3 years out of it. Cost about $40 in materials.

Steve Bellavia
Hobie FX-1, Sail #211