I have never managed to get mine completely judder free in 6 years with the car; adjustment and general fettling have temporarily improved the situation, but never eliminated it!
However since having the new hood fitted I have solved the issue of more water on the inside of the windscreen than the outside.
The other solution is to do what 2 of our party did in 2007 en-route to Le Mans (a particularly wet year). No hood and just aero screens
