Ranger, your mast spool most likely is not the same material as the boat. I've had great luck with 3M Scotchweld DP 8010 (available from industrial suppliers) on polyethylene. Your spool may be some sort of nylon compound, but nevertheless, I would epoxy the missing piece back in, and at the same time, epoxy on a reinforcing piece of whatever you can find (nylon, Plexiglas, ABS, etc) that matches the top surface of your spool, complete with holes. This will provide the necessary reinforcement for your chipped out piece. You can build it in 2 halves and sandwich it around the mast, then sand to smooth.
For your rudder, if you order the plastic screw, you will see the proper size. Once drilled, you can probably use a matching steel screw to thread your plastic hole. If you can't find a picture of the location, I can go and snap one for you.
There are a lot of excellent dealers around. You didn't say what you were looking for -- sales, service, repairs, or parts. I'd recommend calling around and interviewing a few in your region. You can get specific dealer contact info in the Hobie web site. If you have a technical question, put it out on the AI forum -- there's some great experience, talent and innovation around here!
