Good Morning, Peter,
I use the same 105mm El-Nikkor as you, along with Rodagons and Componons in focal lengths to suit different sized negatives. Generally speaking, such high-quality lenses will give excellent results at a variety of stops. Wide open is probably not a good idea unless absolutely necessary, and extremely small apertures may lead to diffraction problems, but I can't see the slightest difference between, say, f11 or f16 when I examine a typical 8 x 10 or 11 x 14. If I need some dodging time, I may lean toward a smaller aperture; if I'm making a larger print, I may use f11 or f8 just because it's quicker.
Konical