I just had the need for a garderobe and luckily I had a 3d printer...
It's a quite simple design and just one screw is needed.
A screw with 3.6mm - 4mm diameter should fit well.
The head of the screw should not be wider than 7.6
After my latest hiking trip to the pyrenees (which is a quite beautiful place that has nothing to do with this hook), I decided to stress test the hook by hanging my backpack on it. The backpack has about 13 Kilograms and the larger hook did not break. The smaller immediately broke apart :-)
But nevertheless for such heavy weight I would suggest to try more infill than 25% - with 25% it bends a little bit.