Command Line Printing - Custom; help ??

[William Case]

Hi; 

I need some help writing script for a special CUPS printing job.  I want
to print on a half sheet of letter size paper.  i.e. 5 1/2" = 396 pts;
by, 8 1/2" = 612 pts .

lpr -P psc-1310-series---1 -o media=Custom 396 612  seems to be the
proper command but doesn't do it.

My printer PPD is:
/etc/cups/ppd/psc-1310-series---1.ppd

It has the following definition:
*FoomaticRIPOptionSetting PageSize=Custom: " -dDEVICEWIDTHPOINTS=0 -dD&&
EVICEHEIGHTPOINTS=0"
*End
*ParamCustomPageSize Width: 1 points 36 100000
*ParamCustomPageSize Height: 2 points 36 100000
*ParamCustomPageSize Orientation: 3 int 0 0
*ParamCustomPageSize WidthOffset: 4 points 0 0
*ParamCustomPageSize HeightOffset: 5 points 0 0

How do I create a non-default Custom definition that I can call using -o
in the lpr command?  Or, however appropriately I should do it?

Regards Bill