Assembling the diferent scenes in an animatied movie

I made a small movie in flash. I did each scene in a diferent fla. Now i’m trying to get it all together. I tried 3 ways.

First I tried to import the several SWFs into a new fla, but i got no sound from the Swfs.

Then i tried to import it all into one fla , but into diferent scenes. Didin’t work cause after about 12 seconds in each scene the sound would start over from frame one. Very strange …

Last, i made a new fla, this time with an mc container to were I load the swf. I have And empty timeline with keyframes with actions. For example, after 123 frames, i have an empty keyframe with a loadmovie action. It works. Just one problem. If i edit the original fla, the swf ends up with more or less frames, and i gives me a hole lot off troble to sincronise it all. And latelly this as became buggy also.

So my question in this. What would be the best way for an animator to assemble all the diferent scenes (swfs) in one easy to preview file?

Thanks