I am designing a scale Kerbal-X in OpenRocket as a potential next project. I will give it a 3D-printed decorative rocket engine on the back of the central tube. However, attempting to simulate the aerodynamics of this engine, by using a pair of transitions, reduces the stability by more than a half caliber. Is this accurate? If not, what could be causing OpenRocket to do this? I have included photos of my simulation with and without the engine bell for reference.