Should I be overly concerned about the limited ground clearance the small wheels at the lower rear part of the Super Z? They look like little wheelie bars and am not sure what purpose they serve. Is the unit so tipsy that it needs them to make sure you don't flip it over? I'm trying to decide whether to go with a Super Z but am concerend about those wheels back there. They definitely limit the steepness of a ditch that you can cross perpendicularly.