I have to agree with DisneyFamily 123. Although it would probably be possible, I wouldn't try. It would be a crying shame to spoil a wonderful signature meal at FF by rushing through it. Any time we've dined at a signature restaurant we have typically taken 1.5 to 2 hours.
Not sure what your dates are, so I couldn't say what the waiting lines for F. would be. Arriving an hour ahead of time will usually get you a seat, perhaps not in an ideal location. If you are going when F. is shown nightly (Aug/Sep) then you might be able to arrive later and still get a seat.
But as I said, I wouldn't try to combine the 2 unless F. had a 2nd show.