Without seeing a picture of your quilt top, kind of tough to give advice. Did you put any borders on the quilt?? If you need to add 5" you might start looking thru patterns to see anything that would compliment the top. There are patterns called seminole that piece at a 45 degree angle and there are many geometric designs to choose from. I just Google this:
Seminole quilt border and just click onto the photos. Hope you see something that will work. There are also free patterns.
Good Luck !!