I could not get the masthead off either, I believe it is epoxied into the comptip.
I replaced my luff track this weekend and this is what I learned.
The masthead will not come off even with the big hammer....
The screwdriver tip in the instructions will only damage your comptip. Dont do it!
Use clamps along the length of the comptip with a piece of tape down the backside(front of mast) to keep the clamps from scratching the mast and apply even pressure along the length until it starts to "pop in". It took me about 6 clamps approximately 8-12" apart and about 5 minutes to do this and I did not even curse. Of course I had already cursed the masthead, Hobie gluers, and the screwdriver so many times I had ran out of good adjectives.
Seriously though, this worked like a charm!http://www.flickr.com/photos/66560235@N04/6253756081/in/photostream