Keep in mind the the torque spec in a manual also takes into account that you are using a fresh star washer, clean and dry hardware, and the same grade of steel nut that came with it. Due to the star washer in this case, a lower torque is sufficient to keep the fastener from vibrating off and all the hardware considerations can be ignored.
Just my experience, but if you are using a flattened or regular washer, to achieve the same amount of "locking" you should increase torque. 25-30ft/lbs should be safe. I believe the thread is M10 x 1.25?? in which case it can actually go up quite a bit higher, depending on the strength of the hardware.