Using a rear motors on a front motor tilting quad plane for maneuvering


I am building a quad plane where the front two motors tilt forward and the rear two stays vertical. This vehicle is an AUV (Amphibious Unmanned Vehicle), the quadcopter mode is meant to traverse in the Air, and quadplane is meant to traverse underwater. When the vehicle is put into quadplane mode I want to use the rear two motors to help maneuver with rolling and pitching while underwater. Does anyone know how I can enable this, or do it manually?

In addition to that I want to be able to transition to quadpane mode while at zero airspeed, this is so the vehicle can change configurations as soon as it touches down in the water. Currently, I am running into issues with the transition waiting for the necessary airspeed, although I have changed ARSPD_FBW_MIN to zero so I am confused as to why it is still waiting for another airspeed to be reached. This transition works successfully if I transition to manual mode, but doesn’t work when I transition to Stabilize. Ideally, I would like to transition directly to stabilize mode. If anyone could offer some advice on this I would be very appreciative.