You should do a ride to Sag Harbor, then Ferry to Shelter Island, and back through the North Fork. Majors Path and Sag/North Sea Tpk in Southampton are decent roads. Like Zuk said though, either early morning or mid-week to miss the "stupid" on the road.
There were quite a few LI Busa riders I've done rides out here with, but I don't know where they went. I'd love to join ya, but the knobbies don't handle asphalt well!