[Jason]

Ditto on the heat shrink - even a heat gun will distort spectra fibers. For chafe guard on halyards and sheets we regularly use a pure spectra cover that yale sells or samson's "Ice" cover or Marlow's chafe cover. The yale spectra cover holds up really well - you can bury it into the core of a single braid line and give it a small whip at the crossover. We cover the eye in the splice as well, burying the spectra cover into the buried tail so that the crossover is just inside the splice. (sounds complicated but you just set up the splice like a core-dominant splice, except you bury the spectra cover into the core before tucking...) But for a backstay, why don't you just wrap it with rubbaweld and call it a day?