The only requirement is DCH 24, Delta Channel 24, MUST remain as the D Channel for all CCS for PRI to function from what I have read in the Legend/Magix documentation.
You can arrange the 23 BCH as your needs dictate. Just remember to delete ANY BCH that are not assigned on the fractional DS1 to the 100D Module. Another point is to make sure you have the correct channel assignments from the service provider per the service order to avoid any complications in turn up and testing.
....JIM....