Thanks, and I did take a look and you convinced me of the hemisphere method, but still; I'm very impatient, so don't like rendertimes to be any longer than needed. Maybe I'll test a part of this scene with the luminous globe, and without extra sun, to check out differences.
What I do use sometimes is an invisible card (luminous of just white or a bit reflective) to light up areas that I find too dark, locally. And very subtly.
Btw. the rockwall on the right bugs me. I don't like it, so I used some local extra definition (by projected SSS, and vdisp, so I didn't have to use a compute terrain), but it's not to my liking yet.