Well, thanks to all responders.

I am only 65 kg, so that is not an issue. I guess I could use the std japanese setings.
Rear shock. Measured sag: 20 mm without rider, 25 with rider. That seems also OK
Hanging off. Hardly anything, so that needs to be improved.
Tyre pressures. I used the same pressures as on the street, did not change them, did not check them just after riding. Again, this needs...
Feelings. I can not feel anything, good or bad on the rear. Probably as the poor things only outputs just above 50. The front was really bad when on the brakes. I could not get it precisely on sharp turns. Two more rings on preload and 2 clicks on compression improved significantly. However I can not say if this is the best it can get or not. Still, when in the sharp turn, the bike does not like the brake to be touched (just for correction purposes, though).

The track is a new one in northen spain, just 1 month old, impressive but not very nice for bikes. If you have a look at the track (www.circuitodenavarra.com) you'll understand.