Hi Forrest, sounds like your on the right track. The first most important thing is to be hunting an old enough area to give you the possibility of old coins. As far as settings I hunt in Pro zero, iron disc set at 28, iron audio always on, and sensitivity as high as it will go. Alot of people would probably think I'm crazy for running my sens. at max but you know what, as long as the machine runs stable I want to run as hot as I can. I get super depth out of the machine and it runs fine. I usually ground balance between 85-90. The next thing I will do if I'm hunting an old park is to find the trashiest sections I can (where most hunters won't go) and hunt them in a grid pattern extremely slow. It's amazing how many good coins are mixed in with the trash, and this is where the ATP really shines. I don't pay much attention to the numbers anymore because the audio response is so good with the ATP for the old coins I like to dig the faint, clean sounding repeatable hits, most of the good coins come from the 6-8 inch range in the areas I hunt. This isn't by any means an easy way to hunt, it's very noisy and down right annoying at times, but it does get results, if you have the patients. Most of my hunts are 2-3 hours max, until I start getting what I call ear fatigue and everything starts sounding the same, than it's time to leave. Hope this helps.
HH Butch NY