Another test for rib integrity is to submerge them instantly/horizontally in a tank of very hot, almost boiling water. The heat expands the air b/t the ribs and forces it out anywhere the ribs are not sealed to the barrels. The stream of bubbles will identify the location of anywhere the ribs have come loose. (Of course, if the ribs are just flopping-loose, the air will escape so quickly you may miss it).

Jim