This seems an odd question, but can you put a Losi hydra drive or Schum viscodrive on the B4 ?
The reason I ask is because of a track we race on in the belgian/dutch nationals. After the first qualifying round, it becomes so bumpy and rutted that driving one lap without you bouncing into something (or someone

) becomes very difficult. And with modern power systems, you really have to have 110% control over your throttle finger.
Now I remember from my first serious race car, the Losi XX, that a hydra drive made a 2wd car more sedated and easier to drive on extremely bumpy tracks, this at the expense of a lot of inertia in the drivetrain. But the drivetrain inertia and extra losses can't be a problem anymore given the modern power systems, much like the phylosophy behind the reintroduction of the XX4.