Same with mine. Shaped wooden supports which have door stops on the bottom (with one side trimmed down take into account the curvature of the roof).
They're 12 years old and are just about looking like they need replacing.
No, but from my reading, there may be some traction in swapping the inner batteries to the outer position and vice versa. This is because the outer batteries work marginally harder than the inner two.
However, it's a very small difference.