The Dux Rampant site seems very quiet so I thought I may have a better chance of an answer here.
There were some unofficial rules /house rules about flanks and ignoring the 3" rule for friendly units.
My main issue is with the latter.
If friendly units can be within 3" of each other but enemy units can't be within 3" how does this impact on units immediately after combat?
I have a line of three units and an enemy attacks the middle one defeating it. Usually that unit would fall back and the victorious enemy unit would stay put. But if the enemy stays where it is he will be within 3" of the other two units, which isn't allowed. Does the victor also need to fall back? How does this work if a smaller unit (strength 6 or reduced figure unit) has friends either side and is being contacted by a larger unit which would then contact the friendly units either side? Does this rule change only work if all units have the same footprint?