FWIW, NTRPolice, I disagree that it is a bad idea to warn your partner of a short lob.
I have had partners explicitly ask me to warn them of short lobs. I give the warning if I think of it, and I appreciate it when they do it for me.
Yes, giving a warning runs the microscopic risk that some opponent someday might claim hindrance and claim the point. Failing to give a warning, however, risks that (1) your net player will be surprised by a short lob, and (2) that partner will dislike playing with you because you throw up short lobs but won't warn.
I think if we took a show of hands of how many people here have ever had an opponent claim hindrance if they say "Short" or "Watch it" or "Watch out" when they hit a short lob, very few people would say this happens.
I think it happens even less at the higher levels because players know that giving a warning is quite common.
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