If you will be using the reloads in non-bottom loading FED or Zorki cameras, you don't even need to trim the leader. You can leave it 'as-is'. The film's leader end can be left as it had been cut from the long roll with squared ends.
This way, you don't have to pull out more film to have sprockets on either side engage with the sprocket teeth.
You would need to trim the film though to a lightly tapered tongue if you use the film for other cameras, SLRs for instance, as well.
Jay