Biannual recordings have a sense of depth with headphones. You can still sense depth with normal music, stuff like Pink Floyd, you can see the in and out panning. But it's not as obvious.
its called tapping and its ideal as long as the metal is think enough..Threaded holes in sheetmetal??? I've used bolt/nut combo.
Bare metal to bare metal is always and will be best.
And after the ground is complete, there's some sort of spray can that you shoot a little of to prevent rust. I have no idea what it is but is def recommended. Maybe a rust prevention or something...?