When you pan and zoom using keyframes, you have to be aware of the settings for the animation path.
Each keyframe can be set to "linear" or "smooth" interpolation. In this case you need "linear".
Take a look at the online manual here: http://help.apple.com/finalcutpro/mac/10.0.6/
You can "print" this manual to pdf using the little printer-like symbol at the top right of the page.
Then open the pdf in Preview and look at page 224.
I've done so and it does work but I'm not sure I like what FxFactory does to the performance. I have the 13.3 inch Mac Pro with lots of memory but I don't have the Invedia graphics card. FPCX has run somewhat sluggishly. This is a problem with my configuration but on the whole FxFactory looks like a keeper, provided I can't find a native solution.
Thanks for your advice.