From: "Herb Martin" <HerbM@[...].com> 

>   * -3.5 HM_URIBL_SC_DBL Prevent SC-SC2 double score
>   * -2.5 HM_URIBL_SC_XS Prevent SC-XS double score

Just set these scores to 0.1 or something tiny like that. Setting them
to minus scores them minus, which you do not want.

{^_^}