Where are iTunes smart playlists stored on disk?

Where are iTunes smart playlists stored on disk?

I want to create a Best albums smart playlist containing a somewhat
reasonable number of songs :
the rule Album rating is greater than ššš result in a 221 songs playlist.
wheareas the rule Album rating is greater than šš result in a 4000+
songs playlist.
I understand why those numbers, but still I would prefer that the
resulting playlist contains ~1000 songs : hence my need to have access to
the smart playlist file definition so I can overwrite the ratings
representation inside.
Other approach tried : activate half star ratings (to create a 'greater
than 3.5 stars' rule), but if half star is activated for song rating in
the main window, it is not the case for the smart playlist dialog.