So the reducer should work well in the visual part of the spectrum to which the CCD is sensitive, though it's uncertain how it will perform at the longer wavelengths the CCD is sensitive to, say 900 nm. A possible further objective for research would be to look into the design of extremely broadband achromats suitable for the whole range of the CCD' s sensitivity, which is about 450 - 930nm. Throughout the above analyses I've decided to neglect off-axis aberrations because of their complicated nature. My experience is that they become a major concern about where vignetting starts to occur. It's for this reason that I've concentrated on the vignetting problem, which is easier to analyze.
Good ray tracing software is probably the best way to fully characterize such systems.
Thanks to Ken Florentino, who first suggested the 75mm x 25mm approach. Thanks for visiting.