[mfranken]

This works but in a very limited fashion. You can send stems, I'd recommend making sure that they start and end on frame edges as MC can't handle sub-frames and the AAF export will contain small sub-frame clips and media. Create your stems in PT then select the tracks to export (highlight track names) and select export AAF. From memory you just need to select MXF as the media type and set the handle to 0 as there is none.

I'm currently working on an animation film doing the same thing daily. We also found that the name of the session you export the AAF from becomes the TAPE name in the metadata of the media that comes back to you from MC once it's done the round trip. This can be used to expand tracks in PT when your stems come back to you in an AAF. This can allow you to say create 5.1 stems that you keep and create stereo stems for MC - so when the stereo stems come back in an AAF you can expand these to find the 5.1 stems, or whatever material you want to expand. It's a bit of work as you need to manually set the TAPE name of your WAV files with an app like Wave Agent, but can really help make this kind of workflow work.

Hope that helps.

Mark