(First bug submission.. hope I'm doing this right.)
The print filters use mpage to build postscript, which has the -t option for duplex printing.
I've added this to the NUP= field in postscript.cfg in order to default the print queue to duplex (NUP=4t)
It would be useful to a lot of people to have a checkbox in the filter selection dialog in printtool that
sets this option for them. It took me ages to find it the right place to put the -t option. (I'm not too hot with lpd)
I am discontinuing all development on printtool, as all new development will
concentrate on printconf and printconf-gui, its replacement. There is some
capability to do this in its underlying filters, and the archetecture is more
maleable than the old one.