Best Way To Attach Paddle Leash?

Got a grab line that runs the length of the deck.

viz: http://tinyurl.com/6z3pxc

The line runs from a bow eye back to the foot pedal assembly.

There's a steel ring on the line that is free to slide for and
aft.

I want to attach a paddle or calf leash to the ring with the
least chance of it coming undone when things go south - yet be
able to attach/detach it with reasonable convenience.

Opinions as to the best method?
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- Figure eight knot that jams in the ring?

- Some sort of bowline?

- Trigger Snap?

- Carabiner?

- Some other sort of shackle?

-Something else?
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PeteCresswell