FCP7 and AfterEffects-WINDOWS: best codec?

I'm about to start working on a project that files will transit from FCP7 to AE on a Windows 7 machine and vice-versa.

What should I look into codecs-wise? I'm sure my usual darlings ProRes and AIC on QuickTime won't do me much good. There's QT on Windows, but AFAIK no ProRes. QT Animation appears to work just fine, but file sizes are huge.

What's the common practice here?

Cheers