This is the one bit of running rigging where shock absorption makes a LOT of sense. Who hasn't jibed and gotten a little more "bang" than they intended, either the result of a mistake or a racer
pushing to save time? Mark stop points that are 3-4 inches off the end stops and rigging loads are greatly reduced (ease to the stops after the jibe).
Not theory. Some of us have been doing this for years, and a number of highly regarded riggers routinely suggest nylon double braid; while not as impact absorbent as climbing rope, much better than polyester.
How is it underway? A little like a bendy mast
, easing an inch or two in the gusts if it's strong, with out making the sail more full. Probably faster than non-stretch.
I tried this right after I changed from polyester DB to Dyneema
(got it free, though it would last a long time). The Dyneema was like jibing against a brick wall and had to go.
Yes, I know that careful line handling is the right way. But have not heard a single
valid reason why a little stretch is not better.