I put in the Southbend Con O after my #5 plate went in. The stock clutch doesn't take much to let go.
I don't know clutches, so I can't claim it's the very best, but this clutch is everything that they claim. It holds VERY WELL, and it is INCREDIBLY SMOOTH, and it seems like it takes less leg than stock. Peter is also very helpful and stands behind his products.
Need more than that?