I have to scream this from the rooftops I guess.
POS-POS print systems have an inherent flaw. You are basically multiplying the slope of one curve by the slope of the other curve, (original slide x print material) to get the final dupe image. If your original has a perfect capture and a slope of 0.3, and if the print material also has the same slope, the result is a slope of 0.09, which is a reduction in contrast. This is why you must use masks to adjust contrast and masks to adjust color.
No pos-pos system without these masks has ever been a big success. Thus, high end labs or printers use masks and get superb prints but at a high cost in time and materials. So, most simple pos-pos printers have failed. Or, they had commercial difficulties.
I know Henry personally and we talked for about 3 hours on his last visit to Rochester. He is avid about what he does, but just like me, neither of us is always right.