I needed a new shaft (foot  holder) for my MC 6600P.  I have a new one but it is different than the one that came on the machine.  It has a screw on the back that sticks out to hold the quilting bar .  The old one has a black metal cover over the hole where you put the quilting bar, and the back  side of the shank is straight with no protrusion. I wondered if it were designed this way because of the Dual feed system.  Does anyone know the answer.  I called a dealer I have met at quilt shows because the dealer i have always used could not get it.  I do not drive out of town anymore.  The dual feed feet on this machine has the shank built in.  No local dealer so have to drive 45 -60 minutes to one.
Thank you for help.