What have you found to be the best place to attach the shackle - I know the ankle didn`t make your short list!
Ha ha, you may be surprised by this, but I like a friend's set-up from a surfboard that attaches a velcro cup around his ankle.
Mine is on my trap harness. My crew used his pfd so I talked him into using a regular sailing safety harness since the pfd is not made to take that kind of load. But there are river rescue rated pfd's that have the appropriate and tested harness equipment built-in. That would be the best idea.
As I understand you, the shackle stays on the sailor along with a pull-cord to easily release/open the shackle pin.
On me that is true, it is on my trap harness and I can clip it to any line I choose. Bill uses a releasing shackle on is teather that stays with the tether.
Bill was considering the polishing you mentioned. I am just going to keep on with the system I have until I find a better shackle.
It has worked for me in various conditions, even if awkward. The most awkward is when you sail up to a dock, stall the boat, and run off of the boat and get yanked back onto the boat.
GARY
