The Tremonton to Twin Falls direction is 700 ft. downhill, so that helps a little. I'd be much more careful in the other direction, although I guess the typical prevailing wind is out of the west, so maybe it's a wash. Definitely use extreme caution if travelling into the wind going from Twin Falls to Tremonton though. I had a close call with a fully-charged S90D in that situation, which seems totally crazy. Admittedly, it was ~0F in January and I started going 90mph because I was in a hurry and didn't think there was any way I wouldn't make it, but boy was I wrong.