Your question was for an optimum Close hauled tack with crew. Not a cruising turn!
First such a tack would not be to 6-9 on the wind indicator, more like 3-4 (40 degree to wind) close hauled.
Second, crew should not use ST at all. Time wasted wrapping and inserting handle could be used for pulling. use Enough wraps for the wind speed on the winch with max pull during the tack and cranking the handle should do it without using the jaws.. Then the tail can be placed in the jaw for securing. Just because a tool has a feature doesn;t mean it should always be used.
Depending on wind speed you should not take all the turns off the old winch, how will crew hold that in 20 knots? Wait until the sail luffs up. I do leave one turn on the winch to straighten out any hockles before they feed to a turning block.
Sails are not backwinded until they fill on the back side after head to wind. This may be necessary in very light air, but should be avoided in heavy air.
The crew should be trimming the sail, not the helmsmen. They should call the optimum angle after the tack.