I am a bit puzzled from the post but I am guessing that you are wanting to insert a graphite shaft inside a steel shaft that is mounted to the putter head. I don't see any performance advantage to doing this. I have tried a few graphite irons shafts in putters and they had no "wow" factor. Perhaps you can sand a .335 shaft down to fit inside a .370. Use a piece of heat shrink tubing to dress up the joint.
