I realize this is a few years later, but I've tried to do something similar. I tied a buntline around the ring, then proceeded to lash it and finished with a constrictor knot around the lashings between the ring and stanchion, but I can't get that to hold. I've attempted a constrictor knot to finish on the stanchion, but it is not quite a constrictor knot as the entry line coming in is coming off of a wrap around the stanchion, so is at an angle. Could you explain how you would lash this, or perhaps a few pictures, please?
Did you do frapping turns before attempting to tie a knot? After the frapping turns, even some half hitches work.
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“It’s a trap!” - Admiral Ackbar.
I just realized having the last knot on the rod, if the ring rotates it unwinds the lashings. I'll have to figure out how to get that knot on the lashing between the ring and rod.