To "time align" the RM40 using the delay functions of the DCX, measurements must be made at the listening position (distance and height) which cannot thereafter substantially change, and the correction only applies to where the mics are placed.
If using a step function for the alignment, you'll note quite a bit of distortion to the waveform from late arrivals, floor bounce, reflections off nearby furniture and the like. An anechoic environment would make things easier, but no one listens in such surroundings, in which the ear is uncomfortable.
Still, it is fun to experiment, so try it and post the results here.