Yes, we want to get the call correct. BUT, remember: 1) Stay true to your boundary lines; 2) Officiate your primary; and 3) TRUST your partner(s).
Yes, there are times when an official should extend his primary but 99.999,999,999,999,999,999,999,999,999,999,999,999 ,999,999,999,999,999,999,999,999,999,999,999,999,9 99,999,999,999,999,999,999,999,999,999,999,999,999 ,999,999,999,999,999...% of the time it should be off ball coverage in the same area that your partner has on ball coverage.
AND, DO NOT be a ball watcher.
MTD, Sr.
P.S. I delveloped a great training aid for officials who want to watch the ball and make calls on the ball out of their primary. It involves electrodes and a heavy duty marine battery,

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