I am reupholstering an old sofa that I am nearly finished with - except the cushion (24 x 72 inches).

I want to make a box-edged cushion with 3/8 inch cording on both top and bottom edges. I have the cord, which has a lip and did a few test runs with the cord and fabric last week.

It was super frustrating. My machine (vintage Sears) is great and can handle the upholstery fabric with no problem. The foot is working fine (I think - maybe thats my problem) but I really think my problem is with the fabric ribbon (lip) attached to the cording.

its super soft, sheer, stretchy fabric ribbon and squishes across the width while I'm sewing. It doesnt seem to matter how tight I pull it or how well its pinned in place. I even dug out mom's "stiletto" to hold it wi thno success. That means my cord is a whole 1/8-1/4 inch "out" from the fabric and the lip ribbon shows - not really what I want.

Is there a technique I dont know of ? I have been watching a billion Youtube videos and everyone on there just zips thru it with no problem, but then again, they dont have cord that has this sheer soft lip ... ALL SUGGESTIONS ACCEPTED (Im almost ready to just handsew the whole danged thing ...)