Encounter/Nanoroute - fixing DRC violations while keeping critical pre-routes untouched

 Hi Folks,

Our design has some timing critical nets, which are being routed in fat metal, and currently my flow is to route these first , fix all DRC violations on these, and then set the "setAttribute -net <net> -skip_routing true" on these nets, so that when I route the rest of the nets, there remain untouched.

The problem I am facing is that when I route the rest, I get DRC violations, and these violations sometimes involved the pre-routed fat wires.  If I use the "editDeleteViolations" command, it will then rip out the pre-routes too, something I definitely dont want to happen.  I did a man on  "editDeleteViolations", and it does have a option called:

-keep_fixed   Does not delete wires marked FIXED in the DEF file when deleting nets with violations.

That option would be useful if I could find a way to mark the wires as "FIXED" in my def, but unfortunately, the  "setAttribute -net <net> -skip_routing true"  attribute does not get saved in the def file.  I cannot find a way within Nanoroute/Encounter to flag a net as "FIXED" and get it saved into the .def so that I could use the -keep_fixed option  

I suppose I could just manually hack the def file to add a + FIXED attribute to each wire, but does anyone know of a cleaner flow to doing what I want to get done?

Thanks