when you have transfered your weight to your "new" standleg, the other leg give you stability and a good, strong body position and at all a good look

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after your weight is transfered your hip start moving to side as a effect of your other leg is straight, turned out and pushing slightly forward, but instead of transfering the weight it transfers your hip to side (have the feeling of side/very very slight forward). this is done at the begining of the "and" beat of rythm. shortly before the next "full" beat or lets say at the end of the "and" your hip turns back and your leg shoot forward to the new step position. during this shoot your leg pass the standleg with a high heel and you have the maximum hip movement. after that start weight transfer again.
In the timeframe your "behind" leg is straight your body is possible to be straight,too, this will make you look more powerful,straight and natural. if your "behind" leg is not straight your body looks lazy and weak.
this technique is very advanced and difficult to do (and to describe), but its used by all top 50 worldranking couples I personally know ... but pratice it very very slow at the begining... this technique with the "shooting" the leg makes chacha very nice and easy.
hope this helps.
(sorry for my bad english)