Checking calibration in MATLAB
The following procedure checks that the two separate camera DLT calibrations work well together for calculating 3D positions.
After you calibrate by marking points on the cube images, merge your DLT coefficients and check 'I need to digitize videos'. Instead of the movie files, load your raw (distorted!) cube images. Digitize some points your cube. Problems with the calibration may manifest as problems to digitize the same point in both views. The blue line will not go through the same point in the second camera view. However, some problems, such as both images mirrored, cannot be detected this way.
It is a good idea to check your calibration in Maya as well.