I think the f75 stock coil is great,,can't complain..I have a few bucks to spend and was looking at the ultimate coil for my f75ltd2...in theory I'm not looking to get tremendous depth,but I'm looking more for clearing up the signal on those iffy 8 and 9 inch coins...I've always thought a round coil would hit those coins harder than a bi axel coil,,,any help from users?