Well, when I am playing with a soft poly I put Babolat synthetic in the crosses. Try to stay away from the multifilaments as you might find that they are too soft and your racket feel like a trampoline (unless of course, you string it very tight, but even then, it's not desirable). To be honest, I don't think that there is any such thing as a "good" synthetic and a "bad" synthetic gut. Just stay away from the multis and you'll be fine for this set-up.