wire size

[osteoderm]

Here in our boatyard, I am always surprised how many boats are markedly assymetrical below the waterline. It may be possible that your rig tune is spot-on, while an irregular rudder or keel could accound for the difference in helm on different tacks.
Go ahead and continue to tune, but don't drive yourself nuts trying to fix something that may be unfixable, and check the bottom carefully next haul-out.