Hi, I am about to install a Garmin Radar Dome 18HD. What is horizontal beam width above head height as described in the manual? I intend to mount it on top of a 200mm tower on the rocket launcher which is approximately 50mm above head height. The bottom of the dome will therefore be around 250-300mm above head height when standing up. Is this sufficient head clearance room as the seats are appox. 1 meter forward of the dome? Thanks in advance.