You want the LED bar further back as LED light is very diffused. This diffusion will light up any dirt or damage at the top of the windscreen glass. This will be very distracting at night, which is the time you'll be using the light. So really you'll need to position the bar back far enough that the roof casts a shadow over top of windscreen. Do some tests after dark so you can get an idea of the exact mounting position.
The other way round it is to move the bar forward of the screen top. I think this looks rubbish and in the fog or rain, will illuminate the water drops, again giving a bright close up dazzling effect.