When you call up a PA piano, you get both the PA piano and Ketron SD2 piano, if the internal on the PA is on. I imagine it defaults to the GM set on the SD2. Rikki posted a way of calling any bank and program on the SD2 from the PA800. It takes a few keystrokes that way, but can be saved as a reg on the PA. The S900 question I don't know.
Bernie