Aaron,
Have you sent in your new CZ-3D to Fisher for them to adjust?
I am very interested to know how this works out, if you don't mind sharing. Let me explain why.
(Long story - sorry)
In the early 90's I picked up a CZ-6a, used it for years and was impressed by it's depth, ergonomics, small overall package and ease of use. It's lone weakness was an appetite for deep rusty nails. I considered it a trade off for the depth. I finally sold it after several years and picked up an Explorer XS. The Explorer had excellent depth with it's 10.5" coil, similar to the CZ-6a with the 8", and it pretty much ignored the rusty nails that the CZ-6a always seemed to find. But every detector has it's weaknesses. I had an injured shoulder fixed a few years ago, but it still doesn't like swinging a heavy detector, like the Explorer, for any length of time. It just gets sore.
I recently sold the Explorer and picked up an older Minelab Sovereign. The Sovereign has a reputation of excellent depth and iron rejection and can be hipmounted. But I need some time with it to see if overall, it meets my needs and expectations. (Everybody has ideas about what works for them and one persons perfect detector is a headache for somebody else) So right now I'm in the process of finding that 'perfect' detector to use for the next several years. The newer top-of-the line detectors are running $1,200-1,500, plus the cost of an extra coil. And in reality, I don't really need all the computerized gadgetry most of these high end detectors have to hunt the places I frequent. The $800 for a new CZ-3D is 30-50% less than top end. The Fisher coils are more moderately priced than Minelabs as well. So IF the Minelab isn't what I thought it would be, I need a plan B.
The CZ-3d is my plan B if I can get a CZ-3D that is up to what NASA-Tom says are the factory specs of depth and target separation. But if it is a crap shoot to get a brand new detector that is what it should be, that is a different matter.
I am anxious to see how this works out for you. If First Texas is willing to get your CZ-3D up to snuff it will make a difference in whether or not I am willing to buy a new one. If they consider your problem the luck of the draw, I will have to decide if it is worth risking.
Thanks,
Rich (Utah)