@tjwspm I've had no trouble using the 828 (35 mm unperfed), 127, and 16 mm rolls and strips from doing this. Yes, it's very possible to cut through the plastic core, but done in a well lit room even this doesn't result in much edge fogging (though it probably would in a film known for light piping issues). Ideally, you'd stop cutting when you reach the core. It ought to be possible to fabricate a cutter with the correct blade spacing for your strip width and blade length selected to have the cutter body act as a stop against the outside of the 120 roll, but the only one I've seen like that is a commercial 127 slitter I have sitting on my desk (at home).
In my experience, 127 and 828 are tolerant of a millimeter or so of width variation, but the width is very even since you're rolling the cut and cutting through the length while you only cut 5-6 mm deep. The 16 mm strip from 127 works in my Minolta 16 format cameras, also -- in all of these cases, the film is driven by tension at the head rather than rollers or sprockets.
In my experience, 127 and 828 are tolerant of a millimeter or so of width variation, but the width is very even since you're rolling the cut and cutting through the length while you only cut 5-6 mm deep. The 16 mm strip from 127 works in my Minolta 16 format cameras, also -- in all of these cases, the film is driven by tension at the head rather than rollers or sprockets.