hi Fran.
what i do is export as a self contained quicktime. yes it's large, but it's a master.
then i run that thru compressor, or mpeg streamclip, or more recently, resolve,
to make an h264, or whatever.
if you don't need that large master file, you can export from FCP as a reference movie.
this really only saves you space if you've fully rendered the sequence.
If you haven't, the render files will kind of go into the reference file and it'll be just as large,
AND you'll have the down-side of reference files to boot.
the downside is that, as they refer to existing media, including render files,
they can become useless if any of that media goes or moves.
so, they're OK if you just want to do a quick down-res or whatever,
but think of them like this: if you need it in a week, do self-contained.
after a certain amount of time, if I'm running out of space,
i might go and delete older self-contained exports.
i do have the sequences they're exported from.
(i archive them in separate projects)
cheers,
nick