When the delta I'm modifying had the fat tires and the blue coro bodywork it was quite heavy. That weight made the one wheel drive tendencies almost unnoticeable. It was possible to ride a straight line with 1 finger on the handlebar. Hill's I can't comment on since the only hill's around here are overpasses but again the weight would prob be a factor. My hope is that the human power on the left wheel which can freewheel when no pedaling is taking place and the geared hub motor on the right wheel which also will freewheel will offer a differential effect for corners and 2wd in a straight line. As I said time will tell.