Scosche magnetic mount on corrugated roads

My Scosche mount has been reliable on moderately corrugated roads, but I found that on really bad corrugations, while the magnet held, the device (a small light phone) rotated on the mount. It seems to me that a dual magnet mount is required to prevent this or at least an elongated mount with more friction. I am aware of and use other solutions for tablets, my question is specifically about magnetic mounts and the rotation on corrugated roads of the sort where 20 kph is a challenge.