Audio Gain Slider in Final Cut Pro
After performing the editing for a student run news program for a couple of years in college, one thing was very evident to me, correcting audio problems can be a beast!. I couldn't tell you how many times I received distorted video on a news segment that would have otherwise been very good. Here is just something to think of the next time you are contemplating audio in FCP.
If you are capturing from a pre-mixed master tape, then all of the audio should have already been adjusted to levels that coincide with the tone media at the beginning of the tape. When you use the gain slider in FCP's floating audio meter to level your audio in accordance to the reference tone, you should be as right as rain.

If you have received a tape directly from the field, even if it has bars and tone at the beginning of it, it is very likely that the audio on that tape will vary from shot to shot. In this case you would also need the Gain Slider to prevent your audio from being hot. Don't be afraid to adjust from clip to clip to tame wild audio.
