Hit with Signum Pro Outbreak for a couple of hours today, and here's my initial reactions.
(Setup - Head Graphene Speed Pro - 18X20, Wlison gut 17 in mains at 58lbs, SP Outbreak 1.18mm in crosses at 55lbs. Previously using WC Silverstring in crosses)
Outbreak is pretty much dead on to what StW suggested. It's round, slick, much like Silverstring, and the gut mains snap back in a similar fashion against it; just a touch less than SS. I found it to be pretty similar in playability to SS as well. Only differences, and they were slight, is that the SS gives a bit more bite, thus a bit more spin. SS also seems to feel a touch crisper when initially strung. However, on the other side, Outbreak is a softer string, and it's a little easier on the arm (which is why I'm experimenting with a new cross in the first place) Outbreak feels like a very soft co-poly. I know some describe it as a hybrid of poly & multi, but to me, it does not have characteristics similar to multis.
Anyway, so far I like it, and it's easier on my elbow, so gonna keep going with it. Will let all know about how it holds tension in the future.