This is a back with high resolution so diffraction (which is not a function of the back but of the lens) will be all the more noticeable.
If you want low diffraction, don't go looking for another back.
Some lenses handle diffraction better than others, but physics dictates that there is only so far that they can go.
If you downsample the image the diffraction and many other faults will be less visible on your computer screen. I doubt that you would find this an appropriate solution to your problem.