The big delrin screw always gets frozen in place. Unless you REALLY want to make an adjustment... leave it alone.
One point on the melting idea: Delrin, when melted, emits a poison gas or fumes I think. Do it in a WELL ventilated place.
Another idea about removing the screw, that works well, is to get a wood drill bit (one of those flat ones with the pointed middle for centering). Use one that is just a bit smaller than the thread size. Usually they have a long shaft and can reach the screw. The centering point fits right into the hollow center of the screw. Be carefull when you drill as the flat bit sticks a little and will chatter, spin up fast and go slow. Also, best if the cam and spring are already removed. Once drilled, the screw threads can easily be collapsed and chipped out with a small flat blade screw driver (with a long shaft of course).
Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA