Well Secret and msterpsichore,
I remember when my teacher told me this as well, he made me quickly stop this by telling me that every time I stick my butt out I will loose all my money, and when I did he dropped a 20c piece behind my back! I STOPPED STRAIGHT AWAY! Maybe ask your teacher to use a method like this!
But I do know that Professionals hips do indeed go past their shoulders, but they do not stick their butts out to do it! They,(in cha cha or rumba for example), place all their weight onto the back foot through their hips and when the move from leg to leg the sort of move their body to the other leg diagonally, mainly because all of their weight goes into the step, to the balls of the feet!
Good luck and hope you get used to Latin!