Thanks all for the responses, I knew you guys would have good input, especially PE. I ran some more tests with Sprint developer and the effect is very faint, but present. I also ran out of Flexicolor fixer so I used a standard B/W rapid fixer for my blix combination. These negatives have a slight purple tint to the base, not a orange/green like the previous tests. Do you think it was the developer or the lack of Flexicolor fixer in the blix that caused this?
This week I am going to shoot "real things" on 4x5 PRO160S (processed C41 normally) and Velvia 50 RVP (processed with Rodinal as I did in 35mm) and compare them. I will post results ASAP.
If I like the results on PRO160S compared to my digital shots (which were too saturated) I may "drop" this idea for now as it would save me a lot of time and testing, but it is something certainly worth messing with.