The Gospels are clear. Nailed above His head. A tau cross would have the crucified individual's head above the crossbar. A bit of a problem, no?
>> “A tau cross would have the crucified individual’s head above the crossbar.” <<
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An obvious physical impossibility. What would hold the body up?
The sag of the arms and shoulders would place the head at least a foot and a half below the bar to which the wrists were nailed.
Ever done chin-ups? does your body just float up?