There will always be problems with the video in fast motion, if you want it smooth.
You only can get used to it.
Most things you could do had been mentioned.
I add this one:
Frames interpolation mode "Adaptive" is theoretically a good, compromise choise.
It switches between Uniform, 1m and 2m while the movie plays, depending on the scene.
It estaminates how badly the frames will interpolate and picks one of these 3 settings.
You could make "adaptive" gear down more agressive. If you want to experiement with that.
Go to the SVP folder (in a SVP 4, its in the script folder), find override.js
open it in an editor and find:
//smooth.scene.limits.m1 = 1600;
//smooth.scene.limits.m2 = 2800;
//smooth.scene.limits.scene = 4000;
If you lower the first 2, you make "adaptive" gear down from Uniform to 1m and then to 2m more agressive.
EDIT:
Wait... Its said, the new SVP interpolates better then the old one. Means, you could also try that.