Cheers for the replies so far.
Capt. Claret
I see what you're saying with the amount of fuselage foward of the CG however surely the vertical fin would more than offset any amount of yaw generated by fuselage forward of the CG?
The book seems to suggest that the downwind engine is critical because (assuming the aircraft is perfectly balanced) the wind from the same side as the live engine will effectively 'push' the aircraft back in the same direction as the wind - hence the mention of sideways force. Still doesn't match my understanding of the definition of yaw.