putting butts forward of the mast drives the bow down (which digs the boat in, usually a slowing effect)... if you have weather helm until that happens you likely have too much rake (again assuming every other trim setting is good)... As a side effect forestay sag as mentioned, it will shorten rake if you tighten the forestay (and eliminate sag). But as was said, lighter air some sag is good, or off wind trying to power up, so you might need to ease some backstay while tightening forestay. By the way it's odd that the boat heads towards leeward with weight foreward... usually weight forward causes steering to windward... that tells me you might have WAY to much weight aft.
A boat with all your weight neutral (centered over keel, forget the driver at this size), and less than 10 degrees of heel, you should have very mild weather helm...
As it pipes up, you get butts on the rail (amidships, because forward or aft affects weather or lee helm), note the mentioning of racers with butts hiking, they are always directed to the rail at widest section of beam (for more righting moment, but also to keep neutral balance fore/aft). If you started with 15+ degrees of heel, and the butts put you back down to 10 degrees or less, your helm should be neutral again... Hence why racers do it... you have the same power, less heel, so hopefully netural helm (meaning less drag) and therefore you are going faster.
This assumes that your angle of attack, your leech, your halyard, your sheet, draft, etc, are otherwise perfect (unlikely)... but it's a start. Others have you looking at trim (as should be)... but your rig tune might also be suspect (especially given that you have new[er] sails).
Its a balancing act of what provides the most VMG... generally sailing flatter is better (to a point), and extra ballast should be centered fore/aft, port/starboard (until you start to heel excessively... you only move weight (crew - pronounced rail meat) to the rail as your heel angles get excessive (which is also something that is boat specific).