I designed several models and finally I got to this model. I failed several times also. Whether pass or fail would be depend on the filament and other environment, so please try passed and failed models on your environment. Failed model has the severe overhang, a little bit less than 40 degree.
Tips;
Nozzle: Kaika high precision 0.4mm nozzle
Layer height: 0.2mm to 0.15mm
External perimeter extrusion width: 0.8mm
This is how to design this model. If you are interested in, please check it.
The author hasn't provided the model origin yet.