I use four chains, two for the car , and two for the dolly.
When I use my dolly, both chains from the dolly to the car are only long enough to get the chain hook over the car tie down eyes. there is very little play in those chains. You don't want the car coming off if the straps break.
The chains that go from the dolly to the MH are long enough to allow turning and they should be crossed from one side to the other. This is done so that they may be able to catch the tongue to keep it from hitting the ground if it became disconnected. JMO