I have a trimmer, never use it. Count back 20 sprocket holes and start my cut between 21 and 20. Cut a nice curve with no tears and you are in business.
If you reload the IXMOO, just cut V-point in one end. It really doesn't need to be perfect, just good enough to snag in the spool notch. Takes longer for me to wind on the film.
EDIT - If you screw up, cut a bit off and start over. Or start your curve back between sprocket hole 24 and 23. It really is not the end of the world. In fact, you can screw up several times and loose very little film.