Groupwise disabling doesn’t work for a very simple case like vehicle wheels, which shouldn’t collide with chassis of own vehicle and other wheels of the same vehicle but collide with any part of another vehicle. If I use traces or sweeps then I don’t have this problem as you always ignore collision with any component of the same actor. But traces/sweeps don’t do actual collision with other objects.
Contact callback from PhysX could be used for this, right? I don’t know what are the performance cost for it, but PhysX snippet for vehicles uses contact callback for all kind of things.