I know, it's so tempting! I have some 'super' halyard line with a parallel core and like 24 cord jacket (VERY fine tight braid) that looks like it might make good stays. I forget what the core is made of, Spectra, I think, ultra low stretch. In 1/4" it's about half again stronger than my 5/32" SS 1 X 19. Does Spectra have the same cyclic load/bending problem? I think if you go to plastic stays, you should go all the way from mast to chainplates!

Jimbo