That'a a tough one, Roger. Minimal stretch Sta-Set-X is a challenge to
splice. I've done 6 or 7 such splices for line currently on my boat,
and easily spent 3 times more effort on splicing it than on any other
two piece line I've done. But, it's the difficult core in splicing
that minimizes stretch, as you know. (If you happen to be using a
Unifid instead of a full fid kit, you might give the real thing a try.
Use some rigger's tape on the end of the core to help get it started,
and thin out the core some if necessary to allow it to bury fully.
There's quite a difference in using the right tools.) The other
downside is that it's not as easy on the hands as other more 'elastic'
types that do stretch once they load up. It'll be interesting to see
if you find a line that does both. My thought is to just use the
Sta-Set-X and a bowline to secure the sheet. True, the knots can
hangup occasionally when coming about, but, it beats having to alway
grind in the last 6 inches every tack - tough on the lower back. Make
up for it by whipping the line ends in a very marlinspike manner.