"Stay Set" doesn't "stay set", and in my opinion 12mm poly rope
is too small and too stretchy for that application. On a Swan, no less!! I do agree with the poster above that if you do end up using that (or please, one size bigger) for your sheets
, then there is no need for the soft shackles -- just tie bowlines.
If I were you, though, I would use double braid racing dyneema
on the inside and poly on the outside, the tightest weave you can find). Have loops professionally spliced in the ends (in both ends) of the sheets if you aren't that skilled in splicing (as I am not).
Then, make your own soft shackles using the "improved soft shackle" method on Estarzinger's website. Even a klutz like me (ropework is not my forte) is able to make a satisfactory soft shackle that way, in about 15 minutes each.
That would be my advice, FWIW.
Soft shackles work really well, are really easy to undo even after having been under tons of force, are extremely light, low windage, no metal to knock a hole in your head
, and are dirt cheap
if you make them yourself -- so very many very great advantages.
However, for use with sheets, they do require an eye splice at the ends of the sheets.