So who messed up here, me or Ellie? Or both of us? And what can I do to correct it? Is it just my inexperience, not yet being comfortable cantering on anything but flat stretches? This was probably the steepest stretch of any length that I've yet ridden, and the only comparable one was a straight shot, and wide enough for 3-4 horses.
Think about yourself going up a very steep incline. Walk would be hard. A slow jog probably harder. Once you hit a good speed, it might be hard to slow down. Not to mention the thought of getting the incline over with quicker.