You can easily try 5" . I hear you when you say you dont have the ability to raise the antenna, but have you considered a telescoping mast. You can buy galvinized pipe in two diameters that will fit togather, set them up aginst your home, raise the inside section a little at a time. Use vise grip pliers to stop it at various height. when you find the height that works, drill thru and pin with a grade 8 bolt.
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