I've had my GU get better with first finger balancing the rims (ie a 6 stud fitment attached to balancer and wheel bolted onto that - not just a cone spun into the rim centre as is commonly done).
And then finishing with an on-car balance on the front tyres - only problem there is once you rotate or swap tyres, unless you mark it its gone, and IMO still never quite the same afterwards if swappign from road to play tyres.