FIT FixedValues

        Clean beam parameters can also be specified by the users, by loading the
    BEAM_SIZE array with values other than its default values (0,0,0).  In  this
    case, no automatic fit will be performed.

    In  general,  we  discourage this usage, as it may result in a very improper
    flux scaling if the beam size is inappropriate. This mode should be reserved
    to special cases where the beam cannot be properly fitted, or to have a cir-
    cular beam by taking as beam size the geometrical mean of the  fitted  major
    and minor sizes.

    Fixing  the  beam size should be associated to the FIT /JVM command to mini-
    mize (but not suppress !...) errors in total flux scaling.