I have a mast for my Prindle with a golf-ball sized dent about 24" from the top due to an encounter with a bridge (don't ask) . Anyway, I did not fix it because I found a good mast to replace it with. I still have it and was considering repairing it. What I was thinking was to shape a 2X4, or a piece of hardwood near the same size as the inside of the mast, take off the masthead, and slide it in to the dent and tap the end with a hammer, hopefully driving up the dent and not getting the wood too stuck to get out.

I also have thought about using a small hydrolic ram. Northern tools sells a small wedge shaped ram and hand pump. I think it is for bodywork or something like that. If it would fit with a bar to spread the load on the good side, the dent may be able to be pushed out from the inside.

Just a few thoughts.

Mike