Hi
You should go bellow the floppy
The installation is very simple. See the manual pg 389. http://www.korgpa.com/pa_root/en/products/pa1x_man.html?en

"With the help of a cross-point screwdriver, remove the two screws tha secure the floppy disk drive cover, and remove the cover itself.
Slide the CD drive into the instrument. Push it all the way in, to make sure that the CD drive mounts to the connector inside the Pa1X (two ‘clicks’ should be felt on your fingers when the connector on the CD drive is correctly inserted).

Turn the instrument on. Go to the Disk mode, and select the CD device by using the Device pop-up on the lower left corner of the Load, Save, Copy, and Erase pages. If it works, go on with the next step to complete installation. Screw screw to secure the CD drive in place. Apply the cover supplied with the Pa1X, and secure it with the two previously extracted
screws."

Franky