How does 67P rotate? What can be said about 67P/Churyumov-Gerasimenko axial tilt?

Is it fixed (if so, at what value), only changing with precession (at what rate?) or does 67P "tumble" with axial tilt changing over time? (and if so, at what rate?)

I'm interested in estimating the 'polar night' area of the comet, and how it changes over time - but without knowing the rotation properties this is quite hard to do.
Looking at this site, there is a table, which has some information.


  Rotation period: 12.4043 ± 0.0007 * hours    


It also rotates around a fixed axis


  recent observations suggest that the axis is tilted about 40 degrees


There are actually only two objects known to rotate chaotically in the solar system - one is Saturn's moon Hyperion, and the other is a small asteroid called 4179 Toutatis (source: this link from Guinness World Records)