Originally Posted by Jim's Gem
How on earth do you do this type of binding without cutting the stupid backing fabric????
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I do this a lot on my quilts, but I still hand sew them down. But to answer your question on "HOW", flip the quilt so the front side is down. pull he backing away from the side of the quilt, trim the batting and front like you need to. Then flip it right side up, use a clear marked ruler and trim backing down all sides to the right measurements you need. Remember check twice before cutting to be sure your ruler hasn't moved.
Sorry you a having all this trouble, Take a break and start again later. If you have already cut this to small then do it the way you are more comfortable with and don't fret over it.