A very little something different.

[Dave_Jackson]

Mart,

I still don't see why two independants are better than (say) a large main rotor with tail rotor, for the same ground box (or trailer).

Consider the drawing at the top of this page http://www.unicopter.com/1488.html. It requires a lot of 'elbowroom' during flight. However, on the ground the two arms swing back to the tail and the two blades swing forward. If the rear supports are detachable, the 'ground box' should be 13' long * 2'-6" wide * 4' high.

Consider its use as a smaller UAV. It lands on some elevated location, folds its 'wings' and uses its cameras to observe the landscape. When require, it opens its 'wings' and fly to get a better view of the situation of interest. ~ Cheap and expendable.

Coaxial is better suited.

The coaxial has a much inferior thrust to weight ratio.

but really you only NEED counterrotation at mu>0.5.

You've got to be joking. You need efficiency at all speeds.