BTW, every non-Tubus rack I've ever owned (including some that are nearly as expensive) have wiggled and swayed under heavy loads. Not so much when commuting, but when I have the grocery panniers filled with canned goods and other stuff that's chock-full of gravity.
That gave me a face-palm moment. I have always attributed the swaying on my bike to the frame, not the rack. So I wondered why I didn't get that nasty swaying feeling anymore when the panniers were loaded, and I vaguely thought something about the loads being smaller or similar. It was until I read what you wrote that I realized the swaying stopped after I put on my Tubus Logo rack.
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Regards