een vrij uitgebreide engelse uitleg over het werken met photoshop files in fcp vind je hier
stukje daaruit over transparantie
The easiest way to work with Photoshop files that you want to lay over video is to create your PS files over transparency, PS’s checkerboard background. This transparency will be honored when you import the file into FCP. It’s important to understand that PS files come into Final Cut as separate sequences. This means that when you bring a PS file with multiple layers, all its layers remain intact as separate layers in a FCP sequence. There each layer can be animated and affected separately.
The only time Photoshop files do not import as a sequence is when they are made up of a single background layer or are saved as flattened images or in some other file format, such as PICT or TIFF. Note: there appears to be a problem importing large format TIFF files into FCP3 under OS X.
Because it’s simpler to work with a single-layer file, I often convert my PS files to PICT images, preserving the transparency information in an alpha channel, a simple procedure and easy enough to create a PS Action for. I retain the PS file to make changes after the following procedure.
en heb je wel eens onder de menu optie modify bij composite mode gekeken?