Donald Qualls
Subscriber
You can get whatever you want in 16mm/110 size by slitting 35mm -- or 120 (which gives you 3 16mm slits or 4 15.25mm slits)
You do have to watch the orientation if you cut 120 into four strips. They'll work in cameras that don't require perforations, but the edge markings will be somewhat intrusive in those that don't offset their frame to clear perfs, and more so if you get them on the wrong edge of the film (load them by the bridge in Minolta style cartridges, where the perfs on single-perf cine film would go).