>>Anyway, in /etc/cups/ppd/myprinter.ppd, I have the following :
>>
>>*OpenUI *Duplex/Double-Sided Printing: PickOne
>>*DefaultDuplex: None
>>*Duplex DuplexNoTumble/Long Edge (Standard): ""
>>*Duplex DuplexTumble/Short Edge (Flip): ""
>>*Duplex None/Off: ""
>>*CloseUI: *Duplex
> 

  Just edit the ppd file and put

*DefaultDuplex: DuplexNoTumble

instead of None

  This sets the default option, but users shoul be able to override it provided 
the printing system knows how to access the ppd, for example kprinter can do this.

You might also have a section like this, which says whether the duplex unit is 
installed or not...


*%=========================================================================
*% DuplexUnit
*%=========================================================================
*OpenUI *DuplexUnit/Duplex Unit (for 2-Sided Printing): PickOne
*DefaultDuplexUnit: Installed
*DuplexUnit NotInstalled/Not Installed: ""
*DuplexUnit Installed/Installed: ""
*DuplexUnit HelpIndex/HelpIndex_15241: ""
*?DuplexUnit: "
   save
     currentpagedevice /Duplex known
     {(True)}{(False)}ifelse = flush
   restore
"
*End
*CloseUI: *DuplexUnit

  This tells the system that the duplex facility is installed on your printer. 
It has no way of knowing so assumes it isn't. I have edited this one to tell it 
the  Duplex unit is there. These advanced options may only be there if you get 
hold of the correct ppd file for your specific printer. This is from the ppd for 
our hp printer which I just installed last week.


       Alex