@MBS I have to apologize for this thread 
As you suspected the wobbles have nothing to do with the trucks.
It’s a FW4 bug caused during detection, here Frank suggests a different T value for detection:
Did detections again with T=1000uS and… the wobbles are gone 
I can’t believe it, 52km/h (32.3mph) without wobbles. That’s a bit fast 
But sometimes it feels a bit strange when almost reaching top speed. It affects both motors at the same time so it is not really dangerous.
After looking at at the logs I can see what the “strange feeling” was. Sometimes motor and battery current drops exactly at the speed where the wobbles started before but I can keep accelerating. The current drops about 1.5 seconds before I stop accelerating at about 50km/h.
or another example
But it’s much greater to ride when you don’t have to face this wobbles 