Boso, I don't know if it was the alignment, changing air pressure in tires and air bags, the steering stabilizer or a combination that made the improvement. But there is significant improvement in all around handling for me.
I don't want to recommend anything as each of us has our own set of influences like weight, wheelbase, tire and air bag pressure, alignment, driving habits and road conditions.
But have you researched Steersafe, Roadmaster and Safe-T as I believe they all have self centering.
2004 Winnebago Minnie 22e(went to a nice family Oct 3, 2015)
2016 Forester 2701DS (Aug 31, 2015)
2015 Camping 3 trips 6 nights
2016 Camping 9 trips 28 nights