What problems will be encountered when modifying the metal transmission shaft MN MODEL MN128?

The original screws of the metal transmission shaft of mn128 will loosen. Modify it like this.
In the fifth picture, the original screws of the metal transmission shaft are replaced with flat head screws and screw caps, so there is no need to worry about the transmission shaft screws loosening.

The last two pictures are the modification methods of the small transmission shaft. Because the screw hole of this small shaft is not penetrating and only has a fixed screw hole on one side (there is no professional drilling equipment), the previous method cannot be used. Only one suitable screw is found for the two holes, and the other can only be fixed with the original black small screw. Although it is tightened, I am still worried that it will loosen!