I would not know about the results from C-41 other than to say that the dye hues would not be correct. Comparing CD3 and CD4 dyes, the CD4 dyes are generally shifted to longer wavelengths and are broader. They also have worse dye stability. Now, this is not so if the couplers are chosen to be specific to the given developing agent. So, CD4 films have different couplers designed to be "correct" with their own developing agent.

The film is "coupler limited" to give this low contrast, so I would expect that there will be some limit you cannot exceed, and even what you are doing should give some crossover.

You might try shooting a step wedge and then plotting the results to see what is going on there. You might be surprised.

PE