Both sides of the rudder housing cracked in the same spot and the sides were flared out considerably. I've bent them back to their normal vertical positions and re-welded the cracks but the housing is rather undersized. I suspect that the rudder places too much pressure on such a small zone of support causing the eventual stress cracks.
Sailing anywhere with the rudder in the tripped/horizontal position would be an obvious issue but the stock rudder is so long and poorly shaped that even lowered in the vertical position it places an enormous amount of pressure at the undersized head in any wind conditions beyond 15kts.
The moral.....check it now-and-then if you're an aggressive sailor.
The solution is to beef up the rudder housing a bit and build a tougher, nicely foiled blade that is well balanced. It'd seem that if time/money are tight then the slightly smaller (and nicer foiled) rudder from the link above would be better matched to the existing housing.