Yes, we did exactly that; we installed a new system and FCP5 on a freshly erased second internal drive
in an attempt to avoid upgrade problems.
Unfortunately in this case, it did not quite work; however everything except capture via Decklink is working great.
Being able to go back to Panther has so far turned out to be invaluable as that’s the only way we can capture
footage at the moment.
OUTPUT via Decklink is not affected so older projects opened and converted play back just fine.