Fisher F2 Air Test

Well even though I have been out with my F2 I got bored with all the rain and did a air test with it. I thought it would reach out a little farther than it did. I could only get a sound about 7"-8" with the sensitivity turned all the way up and about 4" with it al the lowest setting which is 35%. I have not been doing this long enough to know what is a good depth and which is a bad one. But I would think that you would want to go a little deeper than 8". However the speed of this thing is unreal. I put 4 coins out and zipped the coil across them and it picked up each one no matter how fast I did it that was good. I did the same thing with my Bounty Hunter and it only picked up one signal so it has it beat on that one. Does anyone else out there have a F2 and if so what is the deepest coin or treasure you have found with yours?