MatIDs for Treestorm animated trees in Max2012 with scanline - how?

[tricky]

I am so out of touch with the scanline renderer, but its the only way I seem to be able to get a render in a reasonable time with Onyx animated trees. The trees have multisub materials on them, and I need to be able to render a matte for the branches and the leaves so I can tweek later.

What render element should I be using? I've tried multimatte, but that doesn't work - just renders black
I've tried Material ID element, but there don't seem to be ANY options for that .
I've tried individual Matte elements, one for the leaves and one for the branches, but they just render black too.

Uh?

[tricky]

Removing multimatte from the lst seems to have done the trick.