Tonio - are you 100% sure that you headbearings are tight, that the disc is true and the front spindle is straight?
I've used std Marzos and Showas and the only braking judder was when the headbearings were loose......
Also at Donny I raced with one of the forks bent by 1/4 inch...I only noticed back home when I noticed the front wheel was turning left when the yokes were straight....
How much fork travel are you using (cable tie around the slider) and have you measured your sag and preload front and rear before you start messing with the spring rates?
HTH, Paul
Paul
15th year in DD #68 and getting slower by the year
1199, SS800 & 620SSie DD racer