southace said..
I would be worried on headboard halyard! Or jib sheet ropes flapping round but I see the concept!
The headboard should be the safest as it's always under tension.
FAR safer than a bowline with sheets flapping, think about it.......with a bowling, every flap can undo the knot a little or the 'back' of the bowline can catch on a shroud/lifeline.
With a dog bone used like this

The line has to go slack enough between flaps to release the loop and therefore the dog bone. The dog bone can't catch on something to undo as it has to catch on both sides and have slack, pretty much impossible.
I've got some arriving today, can do some break load testing to see how close to the dyneema breaking they are.
whiteout said..
more new age rubbish
Actually they have been around in wood longer than the S/S shackle, and in ally for dyneema for 15 years!!!
So you have 3-strand hemp halyards and sheets? Wooden blocks? Sextant?