Cracked Mast at Spreader

[Brion Toss]

Hello,
First, the mast is already compromised by that crack, so is no longer exactly a continuous extrusion. The question is, how can you restore it?
If I am thinking of the same mast, the spreader bases are not flush with the mast, and they also take shroud loads, with stemball sockets built into the casting; not clear on how you could hope to double this one, except internally, and that would be a neat trick, but would provide strength too far away from that failing metal adjacent to the weld. So I like the grind-it-flush-and-start-over option. Lots of overlap, no stress risers, fasteners as well as adhesive -- it'll be stronger than new. Wouldn't hurt to drill-stop that crack first. And maybe six feet is more than you need.
Once the doublers are on, consider going with a saner configuration, with spreader brackets or through-mast spreader tenon, independent of conventional external tangs. The original configuration was a mass-production convenience, not the best way to do the two jobs. There's a reason they don't make them that way any more...
Fair leads,
Brion Toss