your analysis is very ok but I can't see further study about the relation between the geometry and the resonance effect so to avoid the higher stress at different levels of frequencies
Yes...The work was not that much extensive...The task assigned to me was just to find the frequencies at which quadcopter will not be safe to fly using FEM (Finite Element Method)...May be the thing you pointed out can be carried out in future either by me or some one else.
