Double Sided Printing in Firefox/Thunderbird

[Matt Florido <matt@xxxxxxxxxxxxxx>]

This is the print command configured for my Firefox and Thunderbird:
lpr ${MOZ_PRINTER_NAME:+'-P'}${MOZ_PRINTER_NAME}

I would like to know how to send a command through LPR for double-sided 
printing.  (HPLJ 2200DN using generic PCL 5e driver - FC3)  I can't seem 
to find any resources that describes how this is performed.  The only 
thing I could find that was remotely close was a request submitted in 
for Mozilla 1.5b: http://bugzilla.mozilla.org/show_bug.cgi?id=213461

I'd rather not specify dual sided printing in the default settings 
because it flips all print jobs, including single page jobs.

--
Regards,
Matt Florido
(Newly acquainted with FC3)