One big pain is that the drive door presses onto the CD holder wherely magnets keep the CD held in place; the central spindle is just a smooth "dome". This is a pain as they could have easily put in a normal CD plastic holder to have done the job; I guess they thought kids would prefer to throw the CD in the bay and close the door, rather than putting it in properly. I'm looking into modding this to be better for my purposes.
One other thing, as normal, the system works when the drive door is lowered, however there is no tact switch as per usual, or levers; no, this system has to be different there too - after lots of looking, saw a plastic piece on the middle of the console, the left side of the drive door; when lowered, it cuts the contact between two LED diodes (probably IR ones) - so just put a piece of card or whatever in the gap and the system thinks a disc is present - easy! Here is the gap - in the console, its to the left of the reset button:
Here is a pic of the system, gutted, but working fine; just tested it.
Going to make my own CD holder section rather than using the supplied one as it is an awkward shape.
Ok, made good progress on the CD top section - as you see in the pic, it is flush now with the GameCube one, and with the hole cut through for the GBA game cart too. There is about 3mm or so clearance for the Amiga drive unit.