This paper aims to present a novel approach to design a dynamic positioning system by using a dynamic model based-design approach. The proposed study has been performed to both develop and preliminarily test the control logic that should be implemented on a model scale vessel. Indeed, the proposed tool has been designed for a fully actuated tug vessel equipped with two azimuthal thrusters and one bow-thruster, emulated in behaviour with a dynamic simulator. Thanks to the model actuation, it was possible to design a unique, optimised allocation logic able to fulfil both open-loop and closed-loop commands, sufficiently proved and tuned before the installation onboard. Moreover, a thorough comparison between different design methods, static and dynamic performance evaluation has been carried out. Two different operational modes are tested, and the results are presented: joystick and station keeping.