I don't know about the X1, but on the SD1 and the XD9 the hard disk is not enough: you need also a little frame to hold and secure it in place, so I don't advice you to do it yourself: you'll need the complete Ketron kit and have it installed by an authorized technician.
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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.