Well I am not sure
So according to the manual and from what I have found elsewhere, the screwheads should be on the bottom.
However I have managed to fit mine in with the screwheads on the top (on the front and rear)
As for them running forward or backwards, I guess with the brushless motor I can just change 2 of the wires to make the motor spin the other way so it doesn't really matter which way they go?