Got out the V for a bit testing to collect some data. Pumped the 11x8 RSD coil, ground balanced, picked up a dime I got pretty deep in the garden. Put on the 9x8 stock concentric, rebalanced, couldn't find the dime. Cranked the ground balance half turn to left, was hitting dime solid like 11x8.
Put back on the 11x8, ground balanced, then cranked ground balance half turn negative again, V goes even deeper.
Why ground balance when "not balanced" hits several inches deeper?
May have to do with the 11x8 RSD being a "hotter" coil than 9x8, even though in theory, the 9x8 concentric should be deeper (?).
Maybe because the Vaquero goes to a positive ground balance when in disc mode. Were you hunting in the same mode that you set the GB in (all-metal), or in disc?
Seems odd, but I found that it works best by setting the GB slightly negative in all metal, then when you're in disc, it's closer to where it should be...
I first find neutral GB, then go slightly negative. Too much negative GB, and you'll chatter & get false signals more in disc, especially with sensitivity cranked up past 10. When it's chattering too much, I either back off on sensitivity or go slightly positive on the GB, sometimes a touch of each 'till it's happy again. ^_^
BTW- on the subject of new vs used Vaqueros... It's great to have the lifetime warranty of a new Tesoro, BUT, there are also some decent deals on used eBay Vaqueros right now... I've seen a few that look to be in good shape, with 9x8 coils, at about 1/2 what new retails for. Couldn't help myself but just bought another Vaquero myself; a newer black one with the 11x8 RSD, factory box and all paperwork. Very nice shape and great price @ $325 shipped. Been wanting a black one...
Also, as long as the price was "right" on your used detector, for $50 plus shipping to them, Tesoro will make sure it's calibrated and send it back to you. Hard to go wrong buying new or used. ^_^