The bow can nearly be over the hitch ball, so length is the boat length plus how many inches aft you position the hull. Since the trailer swivels at the ball the bow is fine right on above it. Maybe 6" back without a winch.
Mine is the same as VaBeach1. That includes a swivel tongue jack and a winch. Any less room and the hatch on my tow vehicle couldn't be opened without uncoupling the trailer.
Those are good points. I would definitely want a winch and I would also want it back far enough that I can open the tailgate of the truck without a problem.