I can't speak for my brother, but the optimum for my lenses (All F2.8 or larger) is between 5.6 and 8. Many of my settings at F11 might be for DOF. Because many of my pictures are close to the subject I will use F11 or smaller to assure that it is in focus.
You really have a lot of good pictures. Is the reason you shoot mostly around fll, because that is the sharpest setting of the lens? I would think larger aperture and faster shutterspeed would be better? but there is no arguing with your very nice pictures. You are lucky to live in arizona. Definitely add u to my favorites list.
