Use the down arrow key

then on clones bind them as follows

clone 1 bind down arrow to move forward
clone2 bind down to move backwards
clone3 bind down to strafe left
clone4 bind down to strafe right
main unbind the down key so that pressing down does nothing.

Then do the same with the up arrow key but do it in reverse so they all move together.

leave the left and right arrow keys the way they are so that you can turn your characters if they need to face a new direction.


Hope this helps.