Wondering if anyone has ever used one of these:
http://www.threadstandhero.com/Threa.../imag013A.html
I found it on a sewing/quilting blog. I too have a walking foot that the bar slides around and never stays in place. I don't use the bar too often as it always moves on me. I didn't know if anyone had seen or tried these before. It looks like it might work!!
For those that can't open the link it is a guide that clamps onto the back of your walking foot.
I am not affiliated with the company at all-merely wondering if the thingy might work for those of us who can't get the bar to stay in place!!