Negative1, I've been thinking about your comments a while back regarding the limited dynamic range in your main print due to fading. If the red print has better dynamic range you could set up luma difference mattes for keying (one each for shadows and highlights) for each print and have the red print luma replace the other print in instances where it has better (more) information. That is, darker shadows and lighter highlights. This would eliminate the need for expanding the luma range in your main print which will introduce banding (gaps in your histogram). This approach is non-destructive but would require the black and white points and gamma to first be adjusted correctly in the red print.

Edit: Would you prefer this comment reposted in your other thread?