Thank you all for your replies, appreciate it!
Reason why I get confused is that when I set up my SpyderLENSCAL chart inside, I get really sharp images. Using the same setup (tripod, timer and so on...) I get MUCH more unstable results. I really don`t get this!
Shutter speeds 1/2000+. So the tripod/ballhead should not be the problem....I think....
Get the same results with my D300 (yes, I know it`s old, but I love that machine in many ways :-) and the same lenses (AF- S 400 2.8D and AF- S 500 4.0 VR - last one are not mine though, just for testing).
I experienced something strange also (I`ve never paid attention to it anyway..); using live view outside I saw that after I had tuned to plane of focus, I saw that the screen went in and out of focus - SLIGHTLY. Using live view same way inside, the plane of focus was constant. "Air pollution/turbulance"?
Will use it for nature/wildlife/soccer/bird (from hide) so I`ll almost always will use it on a tripod/monopod (haven`t tried it with a monopod yet).
I`ve read your thread regarding long lens technique, Bjørn, so I don`t try to support the lens with my hand.