Once you cross process your neg slide film in c41 developer try this at the printing stage.

two enlargers, one set up for the negative , second enlarger for flash,

have two easels with identical blades so that when you flash the borders of the print stay white.

print the negative with shawdows printing very cold , won't be hard because the balance will want to go that way.
if the shawdows are green cyan, then flash a slight magenta red cast into the highlight areas. This will be helpful as this type of cross process is very contrasty to begin with so the flash will bring in the highlights and upper midtone.

Basically you will have a print with complimentary colours in the shawdows and highlights.

a very cool effect
have fun