I've noticed that as well. ANd, between you, me, and the fencepost, I;ve heard from other engineers that would just as soon see the older SDs junked than to ever run one again- apparently after time, they've turned into rattletraps. Again, it's who you talk to. As for theories, we're all just tossing stuff out, and one line of thought is about as good as another. Which makes for some pretty good discussions, come to think of it.