Rolf,

It wouldn't take much for the distance between the pole tip & the halyard block on the mast to vary by upto 50mm.

From memory the "toe in" of my marstrom T decreased by 12mm when the rig was tensioned & you would only need 5mm to 10mm additional "toe in" to loose the desired setting on the luff of the kite.

Added to this is the potential of the mast to move forward with the gusts also affecting the distance between the head & tack.

The movement would be noticed (performance wise) after about 20-30mm of movement