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.