As I understand it you're planning to use it as a indexing plate, like the way the Aries
uses a gear
Not as a sprocket, hence no chain.
Seems like a smart way to get a ring of holes easily ... clever fellow !
Just be aware, though, that most high strength alu alloys (in fact, all of them I'm aware of) fizz away fairly rapidly in salt water
. And the others would make a crappy sprocket.
It doesn't stop the latest Optimist masts being made of one of them (7075, IIRC) so it's not immediately fatal, but it might pay to try and get several sprockets the same, to have a spare, once you've decided on what size, and how many indexing teeth.
My only other thought is that it would be easier on the brain to go for, say, 72T, so each increment is exactly 5 degrees. Then if you want to change course 60 degrees, you just go twelve holes.
If you have a drill press, I can describe a crafty, and easy, way of drilling a ring of holes at any increment you want.