Basically everything is 3D printed. I don't know much about 3D printing, but my understanding is that it is printed from industrial grade machine (Shapeways type ?!?!?). Anyway, no, the hull does not flex at all, and it also being somewhat narrow tank, it is very sturdy. There is also no swing arms to speak of (the swing arm is hinged on both side off the chassis) because of the tracks going around the entire lower. Everything is rock solid. The tracks are indeed lovely. I have blued them in the video but very well made. The hull MG indeed can be servo controlled as you can see in the promote video, but I didn't do that in my build.