My shark has interchangeable coils. I was thinking of buying another (used) shark with a hardwired coil and swapping for a bigger, say 13 inch, coil. I was wondering if one of the aftermarket coils made for the Tesoro would work if I could hardwire it in. The lake I hunted hard last season has deep sand beach that I feel has targets too deep for my stock 10.5" coil to reach. There are also very few targets, so heavy trash is not present. Also, the sand there is so mild that it's impossible to actually ground balance the detector, it's balanced no matter where the balance knob is set, incredible but true. Any opinions, information, or observations please.