I noticed in the Garmin 430W Installation manual it shows a drawing mounting the GPS Antenna to the top skin of the plane using a neoprene gasket on the outside and a backing plate on the inside. Were these supposed to come with the unit? All I got was the antenna... I can fabricate the backing plate if I have too and I guess buy the neoprene gasket, I am just wondering if I should have received it with my 430w.