Render Alpha Channel in Sony Vegas

[Michael]

Does anyone here know how I can render and preserve the alpha channel in Sony Vegas? I have tried QuickTime MOV Animation set to 32bpp but it doesnt seem to work after switching the media properties to premultiplied. The only way I can get it to work is use AVI uncompressed and preserve alpha.

Any ideas? I would love to get this working so I aint getting 1.5gb files from a few seconds clip as AVI.

Thanks.