Hey Tortuga,
Rumors of another firmware update coming. Not sure what it might include, but it's nice you have the firmware/software update ability on the GPZ 7000.
Something on the GPZ 7000 vs. GPX 5000. Some time ago I was spending more time with the GPX 5000 with the Coiltek 14-inch Elite searchcoil. I worked the area pretty well, figuring I didn't miss much. I revisited this location with the GPZ 7000 with the 13x14 Super D and found 2 small nuggets around 1/2 Gram each at a great depth and they sounded really well. Due to the response, it really thought they were trash that might have fell off my pick.
I was using these settings on the GPX 5000 (Special-Sensitive Extra) & (High Yield-Normal) on the GPZ 7000.