The way I mentioned isn't really possible in Toribash(I guess) but it is possible in source games and many other videogames.
Again, I'm not saying that the use of twixtor is forbidden for slow-motion purposes. Just the fact that twixtor increasing your fps doesn't make your slow-motion smoother. It's a bad illusion of smooth slow-motion. All it does is create a blend between two frames, giving you a stretched out image of everything that moved between the two frames. You are not meant to see those frames, which is why twixtor's main usage is to increase full speed fps, whereas you can't see the frame.
Don't increase the fps on the whole clip and then slow it down, just increase the fps on the slowed clip by a tiny bit. Using twixtor to create smooth slow-motion is a bad illusion of smooth slow-motion.
You've got to realise that slowing down the clip slows down the frames per second aswell. Making it easier to see each and every frame by itself, that's where you start seeing twixtors fake frames. You should avoid letting those fake frames be seen. And if you're getting choppy slow-motion from stable 60 fps footage you really have to rethink how slow you want the clip to be, or just apply a small amount of twixtor to the low fps clip to get the 'choppyness' away and still not be able to identify the fake frames.

Again, sorry for thread hijack.