I still have a Bounty Tracker IV that i keep as a back up machine and use when traveling to the Philippines , since i have to hunt in all metal anyway due to different metal content of coins, i doubt a 10" coil will do you that much more good . On the other hand i picked up a 4" coil for it and i can get much closer to metal fences and play ground equipment. The 4" coil helps in trashy areas as well. I have since bought a 4" coil for my Fisher F4 as well for the same reason.