I was thinking more of structural loads DAR and as nobody would ever try and land with banner or glider still attached its not really the same. I suppose its how long the bit of string is 30-40kg in a 70 knt wind isn't a straight down force and on the departure roll its pure drag behind the aircraft. Although to be honest looking at the photo the bit of string is very straight up and down.
I would be more worried with it bouncing and it hitting the tail on landing while breaking.
I would have agreeded with you Genghis two years ago until a rather well educated empire test pilot of my aircraft type told me otherwise when I was bitching about the aircraft with the yaw damper U/S. I must admit I got a bit lost half way through the different modes of various divergent oscillations, and which control you belted with a rubber hammer to set them off.
But as you know way more about these things than I. If you say its possible thats good enough for me.
I was very happy with the principle that if the arse waggles and the nose pitches up and down a bit it and its uncomfy it was dutch roll.