This has been discussed many times in many forums. many people have successfully hauled their cars with tie-downs both straight and crossed. There are many reasons why people justify crossing the straps, but straight is the best way to go.
Let me explain.
With the straps crossed the car cannot move, this is true. Also with the straps straight and tight the car cannot move either. Example, pull a rope tight between both hands, now try to move the middle, cant. If the straps are straight and one strap fails, the car is still secure front and rear. It cannot move under acceleration or braking, it cannot also move side to side. If it is secured with the straps diagonally and one strap fails, the car is no longer secure front or rear and is totally free to move in any direction.
The "R" hooks are the way to go and both ends pulling straight.
I know some will argue this, everyone has to do what they are comfortable with, but play with some string and a diecast and you will see what I mean.