Hi john your winch should have a pressure regulator on the f64 this is adjustable so the more air pressure the more the winch will pull, the pull should be set for the weakest link so making it safe.you can change cable thickness by changing the gears and chain in the end.
I think it's law in the Uk that all winches need to have a mechanical shear point before the winch fails the f64 comes with two systems the air clutch that I think yours has and a slip bearing clutch that's not adjustable.
moose