I worked on methods for slitting 35mm film to produce 16mm wide lengths before I learnt of the debate that exists on the topic.
My solution was based upon using a defunct 35mm camera with a slitter built into the back plate. The advantage of this is that you can do the whole thing under normal conditions without needing a darkroom or bag.
I asked my local camera store if they had a 35mm body they could see no use for. I won’t mention what I was given as it is sure to offend someone that I did some destructive modifications.
This camera had some problems and after a short time it failed. Actually, my original configuration would have contributed. That configuration had the slitters working as I advanced the film. This placed a great deal of strain on the winding mechanism. I changed things to have the slitting carried out as I rewound the film.
But now I had to modify my Praktica LTL.
I finally gave up on this approach. The stress on the winding mechanism is too great and the multiple times the film has to be handled is not good. Also I had bought some bulk film.
Now I use a variation on the standard splitters that can be found on the Web:
http://www.subclub.org/darkroom/splitter.htm - the basic one
http://ronp.freeyellow.com/slitter.htm - similar
http://pages.sbcglobal.net/jdelisle/myfilmsplitter.html - complex and uses film in cassettes