Nick, if it is not noticeable in pitch then that must add weight to your drive-train theory since pitch attitude changes are in line with the drivetrain and the Tq spikes are only caused by attitude changes perpendicular to the drive-train.
Steve76 - you have hit on a question that has long been unanswered 'why does the helo turn more easily one way than the other'. I have always found wingovers easier to the right on a US rotation and to the left on a French rotation which correlates to the reduction in Tq when you roll against the direction of rotation. Has TR thrust got anything to do with it? I'm sure it has but not as the major cause.