Weather helm with respect to old woven dacron sails can be attributed to mainsail SHAPE ... ie.: the position along the horizontal chord of the sail where the maximum draft occurs.
Here's an article Ive written on how to 'properly' raise a woven dacron sail and the methods/suggestions to follow so if that this 'proper raising and stretch-out' doesnt correct weather helm then what to do about it. Once this methodology fails to correct so-called WEATHER HELM, then and only then, should the mast be 'raked'.
How to properly RAISE a woven dacron mainsail - SailboatOwners.com