Cutting down from 8x10 produces very little scrap. You can get either a Yale stack cutter or a chinese knock-off and cut a 10 sheet box of 8x10 with the top and bottom card stock packaging protecting the surface of the top and bottom sheet of film. Three cuts and you're done. Alternatively, you can cut one sheet at a time with a rotatrim (emulsion side down) but then you're more prone to problems. I know 5x7 photographers who notch their cut film with a hole punch but I personally never found this necessary. Just make sure to tell your lab which way the emulsion lies in your download box as it makes a difference with c-41 processing.