I did a Tourist II conversion earlier ths year. There were no problems feeding 120 film through it once there was enough room for the 120 spool in the feed side. I left the 620 spool in the take up side, no need to modify that side. It is a dirty process, so blue painters tape EVERYWHERE to keep grindings out of places it doesn't belong. I taped the entire outside plus over the the entire inside except the work area. I used a dummy roll for the many test fits until it moved freely in the chamber. A thorough cleaning is next, compressed air followed by wiping with a soft cloth soaked in a fast drying solvent. I recommend not modifying the take up side, the tabs on the shaft are too small to properly engage the slots in a 120 spool and could possibly slip causing film advance difficulties. The tool of choice for this is a Dremel with a good assortment of grinding burrs. Have fun!