My Hobie 16 also had a mast base that tore itself loose from the mast. It was partly my fault: I had one of those new stiffer mast step hinges, and I was using it UPSIDE DOWN. The ball of the mast base missed the cup, and I levered the mast base right off the end of the mast. Not good!

I bought a new mast base, stop-drilled the cracks in the mast, and drilled four new holes for riveting... you can drill them anywhere you find solid metal, right through the new mast base. The new base is very solidly attached, now!

Rick