As I know from high school geometry lessons, any 3 points can make up a plane. Extrapolating this clause to satellite hardware language, I could say that star-holder is more than enough to hold LNBF or LNB in perfect position when LNB's Phase center is perfectly co-located with antenna's Focal point. Star-holder allows to do so. And there is no need to overmedicate things .... Points are A, B and C, and their positions are dependent on length of the 3 feedarms (in some cases there are 4...
LNBF holder for PFA
LNBF holder for PFA