Best way to stabilize a moving object?

I'm editing a conference presentation with footage from two cameras plus the slides as images. For most of the video, the slide occupies most of the frame and the presenter is in the remaining (portrait-orientation) section. I need to keep the presenter smoothly centered in that window, but I'm dealing with both camera motion and presenter motion (he walks around). What's the best way to stabilize just the presenter (allowing the background to shift as needed)? I'm working in FCPX 10.0.8 (multicam for the two cameras) and have Motion 5.0.7.

Thanks!

You'll need to manually keyframe the position of the clip.

That's what I've been doing so I appreciate the confirmation. A bit of a chore but doable and the results are mostly good enough. I was hoping that Motion or some plugin like Lock & Load might help to automate the process.