In this work we consider the modelling of an innovative modular aerial robot which is obtained by rigidly connecting a certain number of ducted-fan aircraft. It is shown in particular how to different geometric configurations correspond different dynamical properties of the overall system which can be exploited by the controller to better succeed in certain operations. In particular suitable constrained control allocation problems are formulated to shown how the modular system performs in the presence or not of possible extra payload and of force and torque disturbances which may derive from the physical interaction with the surrounding environment.