Hi auchencrow,
Thanks! :-)
I think, you're right: it's better to see how the saddle will sag on the first ride, and adjust the tension accordingly.
Of course, each saddle is unique, so I don't expect to find "scientific values" like nut torque force in Newton / metre, but merely looking for personal opinions.
The Eric Sande's page is very useful indeed; I've learned not to use liquid oils for treatment...