Well I've got an idea. "Back in the days" when I learned Blitz3D there was an option to inverse model's mesh in runtime. So I scaled the sphere up, inversed it's mesh and applied fog that was visible! Creating sky that had a limited vision.
I didn't find any instruction that I could do it in A7. I tried to do a box in WED big enough so that could react to fog, but then i can't see the skybox, and box must be very big too and might take way too much memory. It isn't very convenient. (I'm making somekind of plane game)