What is the maximum depth from which you want to recover a target? I know the whole idea is to go as deep as possible, but do we really want to dig a hole greater than 12" in a park or a yard? I see a lot of You-Tube videos where detectorists are using shovels. Granted, they are narrow and I know they can do a very neat job. But most reactions to our hobby are based on perception, and a shovel is a shovel. "Officer, there is someone digging holes in the park with a SHOVEL!" I know, a careless hunter can make a bigger mess with a knife or a trowel because they don't care what it looks like when they leave. I would personally only use a shovel in a field or in the woods...never in a park or yard.
Back to the original question. I guess if I knew the target was a gold coin, or diamond ring, I might make the effort and go for an extremely deep target. However if I was in the middle of a well groomed park, with lots of people around, I might mark the target somehow and come back later in the evening when there would be less spectators. Your pinpointing would have to be dead on, so you could make as small a hole as was possible. Also, I think a drop cloth is a great idea, as sometimes getting all that soil back into the hole is a real chore. I hate to leave a "dirt halo" around the plug when I'm done! For me, I WILL dig that deep if I can do so without attracting a lot of attention, and if I think I can do it neatly. It's a lot of effort wasted if the target fooled you and turns out to be deep conductive trash...
Back to the original question. I guess if I knew the target was a gold coin, or diamond ring, I might make the effort and go for an extremely deep target. However if I was in the middle of a well groomed park, with lots of people around, I might mark the target somehow and come back later in the evening when there would be less spectators. Your pinpointing would have to be dead on, so you could make as small a hole as was possible. Also, I think a drop cloth is a great idea, as sometimes getting all that soil back into the hole is a real chore. I hate to leave a "dirt halo" around the plug when I'm done! For me, I WILL dig that deep if I can do so without attracting a lot of attention, and if I think I can do it neatly. It's a lot of effort wasted if the target fooled you and turns out to be deep conductive trash...