Customer brought in an old school house map from the 1850's found in her grandparents home many years ago. It has significant damage. She looked in to having it restored by a conservator but the $8 to $10 thousand dollars isn't possible. She just wants to display it so her kids can enjoy it. The top is flaking off the backing which is some kind of canvas. Wants me to glue on the pieces. What kind of glue would you use? Again, this is not a preservation piece. Thanks.