Uncle Dave,
You're right about the PSR9000 keys not pushing as far down as others.. It's like that with almost all of the PSR models. The keys seem to bottom out rather quicky.. I notice that a lot when playing my PSR-550... I remember when I owned the Casio MZ-2000. That board had full size keys, and the keys took more pressure to bottom out too. When I sold that board and bought the PSR-550 it took me a few days to get used to the PSR action again. I was afraid that I'd break the keys....

Squeak