Thanks again, Steve. It was fascinating listening to your horns - such a different presentation and so fast with exquisite micro-detail.
I've set the arm up and given the deck a quick spin. What I hear the ebony armboard doing is negating a slight edginess that the steel board was imparting to the presentation. Nothing too obvious, but I would call it greater tonal expression - making the music more coherent if you like. I will have much more time tomorrow to listen and the SR5 will have fully warmed up again.
For now, quite apart from the fact that it looks superb, it seems that ebony has proven to be an excellent interface between arm and deck.