Question:
What shape should this be?  Is it a rounded triangle or a four- sided kite?
Is the passing back to back principally on bar 2, or does it also use bar 3?

Answer:
The danger in this formation is for dancers to advance too far (almost to the opposite side).  It should be danced closely back to back on bars 2 and 3 and so should not be an angular movement - closer to a rounded triangle than a kite if that is how you want to describe it.  Don’t get too mathematical about the analysis of the pattern but because of the footwork on bars 2 and 3 (moving to the right on both steps) it is probably correct to say most of the passing back to back is on bar 3 when the right foot is leading.

Traditionally this formation was taught so that the dancers should be at least half way through the formation, by the end of the second bar, in order to facilitate the retiral  - that is to say they should be back-to-back, or have just passed that position.