Rear rack attachment system for Bikcarry trolley

As the proud owner of a super shopping trolley from Bikcarry, I wanted to create an attachment system that could be adapted to my luggage rack (a Tubus Logo Evo). The Bikcarry is supposed to be attached to the seat tube, but the attachment system takes a long time to undo each time I use it, and it brings the trolley a little too close to my bike.

Bikcarry sells a system for attaching it to the luggage rack, but 1) it's hideous (a sort of vertical stud sticking out) and sticks out all the time, which limits the use of the rack, 2) it only solves the second problem, and 3) it's quite expensive. 

So I've come up with a new system that fits onto my luggage rack without protruding more than a few millimetres, and which above all allows the trolley to be attached and detached in less than 5 seconds. It uses a magnetic locking system to secure the trolley. To be compatible, the original hook must be replaced by a new one. 

Personally, I fitted it to my rear luggage rack, a Tubus Logo Evo, but it should suit any rear rack with spacers 74mm wide, 10mm in diameter, and 80mm apart. In any case, I'll put the .STEP files here if you ever want to modify them.

Parts named “Bikcarry_Body_*” must be printed in PETG, with a number of perimeters of at least 4 and an infill of 60-70%. The hook, meanwhile, must be printed in TPU to maintain the flexibility needed to follow the trolley when the bike is in motion.

Personally, I've been using this system (and the Bikcarry trolley) to do my shopping for over a year now and I haven't had a single problem with it. The only problem I've had is that when the hook is printed in TPU that's a little too flexible, the trolley can occasionally roll up if you take a big bump or a bend very quickly, but only when it's empty. This has never happened to me when the trolley is full, as it is then weighted down enough to hold it firmly on the ground.