If you went back to the original message and followed the rest of
the thread, he was actually looking for an official, documented way
of creating iMovie effects purely using QC compositions.
You asked about the official supported way to make it work, not to
make YOUR way work - YMMV.
File an enhancement request at bugreport.apple.com.
Anyway, as I guess iLive ยด07 is somewhere around the corner, I doubt
you'll see anything like that before iMovie 8 even if it's honored.
