When I saw this GC clip on Wednesday morning from Bernhard Langer, detailing how he putts without anchoring that long putter, I knew I had to post the video as soon as it was available.
The key is his posture. By making sure his spine is straight and pulling his shoulder blades back to create a very erect posture -- perhaps even a bit more erect than you would normally want to stand -- he's able to stabilize his upper body and make a turn that keeps the putter on line.
This is a case where Bernhard's demonstration will tell you more than all the words I could write. For those of you who really want to keep using a long putter, this video should be all you need to get the technique down and maintain it.
Leave it to Bernhard Langer to figure this out. I wonder if Scott McCarron is using the same technique with his long putter?