I have a Pfaff 1471 (a mud 1980's machine) with a walking foot.
The largest size I have quilted is a throw size (about 85 x 65) and I stitched in the ditch from one edge to the other. The however, however, is that I always start from the same side or same end. It got a bit "thick in the harp for a while" - but it did work.
My reasoning for doing it that way - if the fabric was going to creep, it would all creep in the same direction. So far, my backs have always turned out wrinkle free.