The Whiting cape that I used is a B grade, and it's the first I've used. The fibers are a lot thinner (whispier?) than true heron, but the construct is almost identical. I wonder if the A grade would have a thicker fiber?
I wouldn't have tied it in on this fly as a full hackle, but I think it looks damn fine as a throat / accent.
If you want to try a handful before buying a cape send me a PM and I'll mail off a half dozen or so to ya.
The fibers, for how thin they are, appear to be pretty damn strong, I'll give them that.