[vj]

I think any aid which helps you trace a straight line is good for your path. You must select a hinge though. Moving the shoulders only will create an angled hinge motion without any added hinge. You can use vertical or horizontal. Any will do but the "deviations must be nil."

I use the proaim glasses, a straight line laser, the putting arc, two balls with a one axis (they looked glued together), electrical tape, two tees set very close to the edges of the putter. I use a lot of stuff to monitor the head and face.