Storyline preload handling

I'd love to know more about how Storyline handles preloading behind the scenes with Flash .swf files.  I have some relatively meaty Flash interactions I have built and I have run into issues with getting them to load properly in Storyline over slow WAN connections.  I have followed all the best practices for Flash publishing (AS3, Flash Player 10, 30 fps) and the movie runs great once loaded, but unfortunately, until the .swf is completely loaded, there is no visual indicator to the end-user that the .swf is getting loaded... they just stare at a blank Storyline screen.

I have build a custom preloader into my Flash .swf to display the percent loaded, but Storyline never displays it.  I've tried encapsulating everything in a movieclip and just having the .swf be a 1-frame movie, but that doesn't work b/c Flash Player won't display content on the first frame until the movieclip is loaded.

I'd love to know how to best architect my Flash movies so that they cooperate with the Storyline preloading method.