If you advance frame by frame and you see you have a regular pattern like:
1-2-3-3-4-5-6-6-7-8-9-9
What you can do is set Twixtor Interp Mode to Nearest, and Motion Vecors to No Motion Vectors, and speed to 133.3333% (4/3).
This will remove one of every 4 frames.
make it 1-2-3-4-5-6-7-8-9
So, because you might be off by one frame (to arrive at the duplicated frame) you can create a nested sequence of the clip, and apply Twixtor to the main (parent) sequence. Then if you are off you can just slide the clip a frame at a time until you hit the right beat.
The net result will be a movie 1/4 less duration. From there it’s normal Twixtor slowmo (75% speed). This will require double nesting or a first pass render that you reload.
Pierre