I ran a quick comparison study of C means weighting methods. I changed the weighting from being (|Dist|²+.1) to (|Dist|³+.1). Below is a comparison of the invariant mass histograms.

C Means Dist³                                                                                                                            Dist²

I didn't notice the difference in passing events before, and really can't explain it. The Dist² peak is stronger and tighter, and therefore likely more useful.