Arm, thanks for the photobucket info, I'll give it a go soon.
Back to the question - No! moving the TR down relative to the MR doesn't increase the moment arm - it decreases it because the moment arm is the distance vertically from the TR to the C of G - this is what Nick and I have been trying to get across. However, it does increase the roll angle because the TR force has a shorter lever to affect the c of g.
Try this - if we don't correct for TR drift and allow the aircraft the slide to the right, the height of the TR above or below the aircraft c of g will determine the roll angle - if it is at the same height as the c of g there will be no roll. This happens without any couple. Since the c of g will tend to be lower than the TR in most helicopters the TR will not only provide a translation to the right (presuming we are holding the heading and not allowing the aircraft to yaw) but will also tend to roll the fuselage to the right - the higher the TR above the c of g, the more roll to the right.
Now we apply left cyclic to stop the drift which rolls the fuselage left because the horizontal component of MR thrust is above the c of g. There are two rolling forces, opposing each other and when they are equal the hover attitude is decided. The vertical component of MR thrust may either help or hinder either of the rolling moments depending on the position of the c of g laterally but is a bit part player compared to the main actors and is primarily there to stop the weight pulling it all onto the ground.