I think that the cd-drive itself is incompatible with ide interface or idefix, because when I used my external usb cd-drive the idefix recognized it perfectly also as in your case it recognized the slim cd-drive.
I'm actually waiting for two drives to arrive at my post office, one of them used to be in a A1200, so it must be compatible. Thanks for all the info, have to wait the for drives now :sealed:...