I don't know the exact science behind this or how to get it to work for you, but I'd like to point out that Krita has a great function that mimics Paint Tool SAI's stability.


http://oi61.tinypic.com/29z5ssj.jpg


http://oi59.tinypic.com/2md6pj.jpg
Move the points around and create new points. Keep trying til you get what works for you.

This setting currently works for me, this is an amazing feature and was the determining factor for me in keeping Krita around.
I am now currently in love with Kirta..I can't get enough of it!!

Those settings are for pen pressure sensibility.
The ones for pen smoothing (or stability) are in the Tool Options docker.

Where is it that you find these options, jpalacios?

http://imgur.com/sxWj6hr