Swinging beyond a "hit" can indicate continued length. That helps avoid digging the /a pipe again. (So says the guy that discovered the same run repeatedly, by digging...).
You won't get readings below a pipe (never say never though) but you can get mixed signals at times above if you are in sync with your detector.
Hearing the iron a little ,just enough to know it's there , would be my goal. Without discriminating it completely out. IF it even could be discriminated out.
Might be worth experimenting by swinging coil above the ground surface a couple- few inches. Despite our usual wanting to scuff now and then to be close.
Not trying for max depth on max sensitivity , but rather trying to thin "cone" angle and just sniff the top few inches of soil above a known pipe run.
