Originally Posted by MadQuilter

Not using a walking foot may cause the different layers of the quilt sandwich to be transported at different speeds causing a shift. On a small quilt it may not be as noticeable. On a larger quilt you have more space to travel and any differences become more easily visible. You may do just fine without the walking foot as long as you make sure the sandwich is real taught.

I have a built-in walking foot on my machine and I can tell the difference when it is not engaged. All of my quilting is Stitch in the ditch (along the seam line). My Free motion skills (where you drop the feed dogs or cover the feed dogs in some older machines) is SO BAD that I haven't even made it to the "I SUCK" stage. More practice needed to get there. lol

Have fun with the biggy.