Regarding the plank wear on the Red Bull:
i believe that they actually can run very low, but not because they cheat or use a trick on the plank mounting or chassis. I'd rather say that their aero platform is very stable and doesn't bounce. And thus they won't wear the plank while (not) bottoming out. In contrast the Mercs and Ferraris need to lift their cars or else they introduce bouncing and thus excessive plank wear. This will obviously compromise their aero efficiency and car setup and lead to a overall slower car.
So as long as the other teams can't figure out to have a stable aero platform - even if that sacrifices peak df - they won't be able to catch RB.