FYI…According to the Field Service Guide, the final “actually used” Media Feed Step in the Epson 7900/9900 is calculated as follows:
PAPER FEED ADJUSTMENT (990.6mm service adjustment) (this is the “base” calibration for the paper feed mechanism)
+
MEDIA FEED TABLES (media feed offset as defined in each Epson media type)
+
LFP REMOTE PANEL 2 MEDIA FEED ADJUSTMENT (writes the offset value to the printer modifying the Media Feed Table value for the specified media)
+
CUSTOM PAPER FEED ADJUSTMENT (Control Panel)
or
PAPER CONFIG FEED ADJUSTMENT (in the Driver)
=
MEDIA FEED STEP
Perhaps this will help answer some of your questions. The key thing is to understand that it’s important to start with an accurate Paper Feed Adjustment (990.6mm service adjustment) since all the other adjustments are offsets (adding or subtracting) on top of that. If you use the printer for doing paper prints as well as negatives, I would use the recommended paper for the initial 990.6mm adjustment. Then you can tweak for the Pictorico using the Paper Feed Adjustment in the printer Control Panel.
FWIW