If you cut it in half and seam it, it will be 54 x 84. That's only 2" short and if your fabric was cut generously, maybe even bigger. So, if you cut it 56", the other piece would be 52". Just put a 4" piece from that extra side bit and then sew them together down the middle. That 4" piece would end up close to the binding and wouldn't even show. Just my two cents.

I have to go out north Monday, so I'm going to take my 3 yard piece and see if I can come close enough that it won't look obvious. Since it's my first quilt, there are multiple errors. I would prefer not to add any more. On the other hand, I'm finishing it, no matter what.

bk

Or you could just buy enough of a new fabric and put the too-small piece into your stash ;-) Incentive to start another quilt :-D

You could also get a nice, complementary fabric, add it dead center to the backing and make it a focal point. Just as if you intended that from the get-go.