Originally Posted by mathteacher
I wonder if your edges don't match because of the natural push of the presser foot on the top fabric. If you pin at small intervals, that should help.
That's what I was wondering. If you have one piece a little bigger than another, always put the bigger one on the bottom and the feed dogs help you to ease them together. So maybe this is because you have too much pressure on the presser foot and it's pushing the top through faster than the bottom.