There are no limitations on installation height as we state on each case     ' Mount the higher the better' due to the curvature of the earth. Mast shadow applies to all reflectors as the mast prohibits the interrogating radar from seeing the complete reflector. Below is a chart of mast shadow.

As there are variables if you take 22/24 degrees as a mast shadow on a typical 30ft yacht with fitted with an EM230 them you will not be far out.