An extensible frame adapted to receive and maintain a rectilinear container applied upon an interior ledge extensible frame. Two or more orthogonally aligned sensor assemblies are provided to measure deflection of panels forming the container when a static or dynamic load is applied upon an uppermost panel. Each sensor assembly outputs a signal corresponding to a deflection of a panel induced by the load applied upon the uppermost panel. Signals output from the sensor assemblies are received and processed by an output processing unit in either a human cognizable or machine readable format. The amount deflection measured by the sensor assemblies corresponds to an amount of bulge of a panel when a defined load is applied.