FPS Question

OK, being new to flash, I build a fairly long web presentation at 24 FPS.

Now, I’m running into some issues with processing on some slower Macs–things run slow (basically any alpha channel effects).

I’m thinking that one thing that might help would be a lower FPS (15 or so) to reduce the load on the processor. Problem is, since I created the movie at 24 FPS, changing it to 15 slows things down on faster computers–to get it back to the intended speed I’d have to basically rebuild it, making it 1/2 the number of frames. I think.

So…is there a way to change the FPS of a movie, while -preserving- the original speed without having to rebuild the thing?