Smack on as they say.
It does not matter which way the front or rear rotors rotate, a long as they contra- rotate, then the net effect IS zero.
They will either precess jointly to a high point over the centre of the fuselage or to the front and rear of the discs (depending on rotation and on which side of the fuselage the deck lies). Neither of these will affect pitch or roll attitude.
That was one of my points although I may not have put it over very well - If the Chinook is moved to or from the deck sideways, fuselage oriented in line with the ships hull, the net effect is nil (the benefit of the ground effect on one side but on the other side the benefit is lost) and no drift will result (in perfectly still air, impossible practically but you must start somewhere).
Now think on the V22 (effectively a chinook flown sideways) and that is why it seems it might be better to approach or leave the deck at 90 degrees to the hull.
All achedemic of course, as has been said - wind of even a light amount will change things, and if the ship is moving, likewise.
SPS late on Sunday night!