I have been using my Ace 250 for about 8 months now and although I really feel it an excellent machine, I am having difficulty with certain trash targets, especially, metal bottle tops, which register as dimes and give off a very coin like signal. I do realize that digging trash is part of MD'ing but I am getting more and more frustrated with these pesky trash targets. Is there any way to tweak the Ace to help discriminate these out without rejecting dimes?