I can not afford the latest and greatest digital backs, but I have always been impressed with the Kodak DCS Pro cameras dispite a number of "cons" against it.
It does great with skin tone once you tune down the magenta, and white balance could not be easier.
Funny that the camera back is one of the oldest I have, yet it is the only one that is sync'd to the on/off switch of the body.
Looks like you would be having an substantial crop factor to deal with on 6x8. You are using the center of the lens for sure. Saw previous comment and maybe its the tilts and swings of the Fuji that
cause issues when using a kodak?
Also I've seen an listing that some mods are required to get the Fuji to sync with some digital backs if you do not have third party (Kapture Group) connectors.