I have a Merida Reacto 4000 with carbon seatpost and alloy saddle rails. There's no torque rating specified for the bolts which clamp saddle onto the seatpost.

What torque should I use for them?

I've tried 6 Nm but it doesn't stay fixed on bumps. I can try increasing it by 0.5 Nm if nothing else works but would love to know the general idea for any such unspecified bolt.