I would look at the available .pin files (these are plain text files)
in the 5i25.zip archive ( in configs/hostmot2/ ) and see if you can find one that
has the step/dir pins in appropriate places, then flash the 6I25 with the matching bit file
The utility that writes firmware to the 5i25/6i25 card doesn't care where the firmware file is located
as long as you provide a path to the file on the command line (so its easiest to run mesaflash from the
directory containing the bit files)
if theres not a matching xml file for pncconf to support the chosen config, I would just use the probfrx2
pncconf hal and ini file and fix any discrepancies in those files (there should not be many or even anyy differences)