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Carbonfiberboy: I started doiing daily hamstrings stretching exercises. I checked your links and integrated a few of the mentioned exercises in my daily stretching routine. At the moment I stretch 2 times a day. I could be wrong as I started only a few days ago - but it seems that in the moring when coming out of bed there is less (almost none) lower back pain any more. Last ride it felt better as well after the ride. I will keep stretching the coming weeks to see if things get better. Currently I'm learing why muscles get shorter at all (adaptive shortening) - I do sitting work and a lot of bicycling...
I got my new 120mm stem today, so if calculated correctly this will move my handlebars 36mm forwards.