Comment 7 for bug 593955

@Wayne,
Why simple to say assume 50mils it is 1mm. Use 1mil as internal unit. All conversion from mm to mils and vice versa do apply that 50mils it is 1mm.
Then pre-printing/plotting if selected 'Units in mm' then print/plot 50mils as 1mm.
In GUI show
100mils - 2mm
50mils - 1mm
25mils - 0.5mm
and ...
I have the same situation that Victor.