So, i am currently working on a script that drives a hovercraft. I have a scene where there are 4 spheres all of which are rigidbodies that hover above the ground. These are connected with fixed joints to form a rectangle. This is the base of the hovercar, but i need an object in the middle to connect the four points, so i can place the body of the car there. How would I do that?
Make a gameobject there and connect the 4 points to it with joints as well? 
I’ve tried that, its too unstable. The box jumps around and collides with the ground making the whole thing stop and spin out of control. I need a smoother way preferably that does not effect the objects at either corner at all.