new back?

[Arnold Schnitzer]

To amplify Ken's point above--the main problem is that flatbacked basses usually have crossbars running 90 degrees to the back wood. This is considered a no-no in woodworking, because wood expands/contracts mainly across its width, and cross-grained joints will blow themselves apart when the weather changes. (Or, if the joint does not fail, cracks and warpage will be the result.) Crossbars are the reason flat-backs fail.