OK, this part I understand. I can see how a main movie and an inserted movie clip would need to run at the same speed, ie. same fps. But I have a question in regard to tweens and I hope it's not too confusing.

Do the main movie and an inserted movie clip have to be set to the same number of default tweens to operate?

When you insert a movie clip into a main movie, the movie clip operates on it's own timeline, right? So, I would think that the default tweens could be set seperately for both the main movie and the movie clip, but that doesn't seem to be the case for KM. I have a main movie with default tweens set to 6. I insert a clip with default tweens set to 12. Once inserted, the default tweens for the clip are re-adjusted to 6, the same as the main movie.

Now, say I want to speed up the action of ONLY my clip but not the rest of the main movie. If I try to re-set the default tweens for the clip to 2 (for instance), KM also sets them to 2 for the main movie and vice - versa. The only way I can adjust the tweens in the clip is to re-set the tweens for each individual frame to 2. This gets tedious if the clip has a lot of frames. Isn't there a better way?