Flash walk-on problems

Hello,

A few months ago we had a local company design a series of Flash "walk-ons" for our website--digital spokesperson with transparent background.

The problem is they only gave us the FLV files encoded at 400kbs, which we eventually realized was causing too many re-buffering issues with too many people. So we called them back, hoping they could send us some new FLVs at lower bitrates, only to discover that they did not preserve the original green-screened avi or fla files.

I have a simple program (Ultra Video to Flash Convert) that allows me to convert to lower bit rate files. Problem is the converted file now has a black rather than transparent background (the alpha info was lost?).

I know very little about Flash. Does anyone know if there is a way to reduce the bit rate of an FLV while preserving the transparent background? If so what program do I need? The company that designed these vids is unwilling to help.

Thanks!