How does this heater box retainer rod (J-hook) work?

Yeah I just ficked one up from a FABO member. My heater box had the area with the J hook hole missing, I repaired it with fiberglass resin and mesh, I am wondering if the j hook is going to break through my reapair at this point, I am not sure but that area looks "reinforced" from the factory. Obviously didnt last forever though beecause alot of heater boxes are blown out in that J hook hole area.