How do I change the default settings in a printer's Default Settings Preset?

Question

I am running Mavericks, printing to an HP LaserJet 4050N via IP.  [The following behavior takes place whether the printer's internal settings are set to Duplex Printing is On or is Off.]
I would like to set the default to print duplex, whether I am in an application or 'drag and drop' a file onto the printer icon (which temporarily opens the application, prints the document, and quits).
I do not seem to be able to modify the "Default Settings" Preset to specify duplex printing.  However, I have been able to create a new "Default Settings-1" Preset that specifies duplex printing.  By selecting the "Default Settings-1" Preset, in any application, I get duplex printing without any problem.
First -- problem:
If I drag-and-drop a file -- e.g., .pdf or .docx -- onto the printer icon, it opens the application and uses the "Default Settings" Preset -- not the "Default Settings-1" Preset -- and prints single-sided.  How do I get drag and drop to use the "Default Settings-1" Preset to get duplex printing?
Second -- issue:
Bizarrely, if I am in an application, select "Show Presets", select "Default Settings-1" and click on "Layout", it sometimes shows that "Two-Sided" printing is "Off" and sometimes that it is set to "Long-Edge Binding" -- but that seems to have no deleterious effect on duplex printing!
Any suggestions / explanations for my problem / issue?
Thanks much,
Avi

Answer 1

Other than using the CUPS interface, http://127.0.0.1:631,which it sounds like you've done, I don't think there is a way to edit the Default Settings. The standard approach is to create a preset, the solution you've found.
For drag and drop printing, you should be able to get to the print dialog and select your preset or turn duplex on by holding the option key down, selecting the file, then doing the drag and drop (either to a printer or to an open printer proxy application).
I realize this isn't a solution, but I hope it's helpful.