Matte magic/matte choker not having any effect

I'm pulling some greenscreen keys with Primatte, which seems to be doing a tremendous job of it, but I'm still getting some jagged edges.

There's some cases where I apply "matte magic", spin the sliders, and then nothing happens. Is there something about Primatte that interferes with matte magic? Or is it something funky with Motion and I should trash my preferences or re-build things in a new project file?

Just an addendum - Depending on the Primatte settings of matte density and noise reduction, sometimes the matte magic filter works.

Is there a connection between how much influence the Primatte settings have and how much influence additional filters will have?

And even better... is there a motion-based tutorial on Primatte and pulling clean keys out there? Everything I'm finding is for Shake, which, unless I'm seriously mistaken, I don't have as part of FCP Studio 2.