any idea how this will affect the handeling?
If you take other bikes into consideration, More rake makes a bike handle better. Too much rake is bad, and makes it want to flop over when you put the kickstand down.
One thing that I did when raking out the neck was to lengthen the backbone 1.5". This should...on paper... bring the trail back into reality...for a bagger.
One thing we noticed a few years ago when I had the opportunity to put my B&B into the wind tunnel was that with the fairing tilted back between 5-9 degrees, the bat wing fairing creates about 60% less wind drag. Too much tilt of the fairing causes the wind to catch under the fairing creating lift. Hopefully the decrease in wind drag does not create too much lift on the front end causing the front end to light and create a front end wobble.
Now to really answer your question......it is a big crap shoot