Got a 10x12 DD for my Vaq...pinpointing was kicking my you know what.
I have found a much larger sweet spot with this coil, and it was not easy to really hear the absolute strongest tone.
Seemed about 6-8 inches wide.
Now, with practice, I have narrowed it down a lot.
I have found pinpoint center on the DD is slightly forward of center.
I did notice a few times a double beep on a sweep, and I finally figured out the target was at the very front of the coil and the quick double beep was the 2 fields passing over the target.
Evidently the fields come very close together on the heel and toe of this type of coil.
Then I found this video and tried this technique and I am having much more luck pinpointing now by quickly pinpointing down to the center of the coil area first, then walking around the target and inching the front of the coil to the target from at least 2 different angles to really zero in.
Does not take long at all with practice.
I use a Propointer, so if I even come close to pinpointing a target I can quickly find it if it is not too deep, but I still want to get better at just using the detector for deeper targets and just in case the propointer goes bad on a hunt.
(Heaven forbid!!!)
This is about a Garrett coil, works the same with mine.
http://www.youtube.com/watch?v=l-hqvdjRVxc