There is a locking tab washer between the thick keyed washer and ball joint and you basically have to snap it by turning the round ball joint body.
So pipe wrenches or speed wrenches are the order of the day. You could grind some flats on the side of the thick washer to make sure it is easier to hold in a vice so it wont turn.
I could dig it out later and take some piccies of it in bits if you think that will help. To answer your question though I would not describe as easy but with the right tools not very difficult either.
I have had a look at it and thought brute force was the method
I've modified one of the Spider racks for GTA and just wondered if it would be better to swap the ends if I could source the shorter version on the GTA .
Seems not ,I'll stick with the current method .
Does anyone know whether it's at all possible to undo the inner balljoint and replace the nylon bush with the rack in situ on the GTA or is there simply not the access?