Could you send in a photo of the damage, or at least describe it's size and location on the mast? I saw someone sailing with a large dent near the base of his mast. When I asked about it, he said that it had been there when he bought the boat 10 years before, and hadn't caused any problems. Maybe welding it would make it weaker more than help?? A photo or description would help some of the experts on the list answer your question in a more informed way.
Is your trip to Key Largo still happening?
Jack Hoying
Fort Loramie, Ohio
Prindle 18 #1645
http://www.bright.net/~jmhoying/sailing/prindle.htm