I have never seen this done and wanted comments. A 100 amp subpanel fed from a wire connected to the main lugs of a 200Amp Main Panel Box. The main box had no spaces for expansion so I assume that is why they used the main lug connection.
If I understand you correctly, it’s wrong.
Absolutely no good.
No way! Why on earth would someone want to loop 4/0 aluminum?:roll:
Double tapping is double tapping and this is double tapping. Fire hazard due to the double tapping of the wires.