Its all down to the installation - get a good installer, and I think Clifford are the best.
As for closeness, depends how you set it.. 1m if you like.. mines probably 6inches from the bodywork.. not entirely sure.
You have to remember tho, it emits a circle ball.. so if you want the bonnet and boot protecting.. then it has to be quite high and sides will go off easily. Where I have mine, is just about right - you can ask the installer tho to set it how you like!