I am working on a drone design based on tri-rotor. The difference between this design and a tri-rotor is that it has an extra propeller in order to generate additional thrust. That's why I cannot use the open-source autopilot ArduPilot anymore. I have prototyped a control algorithm on MATLAB/Simulink but I don't know how to implement it on the drone. How should I do that? Should I modify the source code of ArduPilot, or it can be easier to start all of this from scratch?