More headsail or less main.
Put simply a main sail drives your bow up to weather and a headsail pushes it back down again. To attain no weather or lee helm your sails must be balanced. So if you have a full main up you want a matched amount of headsail to keep things happy, if the wind is strong enough to warrant less sail forward then you should also be shortening your main.
Not the most scientific answer your going to get, but I hope it helps. Enjoy the new sail, I am very jealous.