By the way, my own mistake: the fin is not 100% symmetrical at the back. This was my own mistake. Fortunately, double-sided tape was used here, so it is still possible to hang it straight. Maybe I will fix it myself soon.
I removed the original handle (protection) because it absorbed far too much moisture. I saw in one of Sven Kroll's photos that he used a handlebar tape for this and I have now done the same. It looks & feels better.