The 7" concentric is really good. I need to use it more. I agree about coil selection. Nokta Makro makes just about every coil size imagineable. And affordable too. (Unlike Minelab and Deus).
99 Sensitivity though? Dang. My ears are too sensitive to the chatter.
Speaking of chatter, my new Anfibio, is very sensitive. Wow. I had to turn the gain down to 70 and the disc up to 10 to quiet it down. But that's in Mesquite, NV. It's a chattery kind of town.

Cheers!