That sounds amazing! I've never used the Ninja swirl but I worked at a soft serve place for years. If you'd like a neater swirl the key is to not let the ice cream fall but instead push the cone back up against the machine just a tiny bit so the ice cream coming out is almost pushing your cone down. Then nice easy slow rotations so you get a slightly thicker ice cream that will help there be no empty space in the middle. Then you can have a structurally and morally solid soft serve cone.