Bill,
I think you can safely install them: you are not going to do any harm to your keyboard. The worst thing that can happen is that the 9000 won't recognize them, but it's unlikely. Anyway, the Yamaha dedicated RAM is so expensive that it was worth the try however.
Have a great Christmas with Jann and Rocky.
Andrea
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Korg Kronos 61 and PA3X-Pro76, Roland G-70, BK7-m and Integra 7, Casio PX-5S, Fender Stratocaster with Fralin pickups, Fender Stratocaster with Kinman pickups, vintage Gibson SG standard.