There is the saying in Xingyi:
Step into the middle door even immortal finds it difficult to defend.
But this is not so easy to step into the opponent's middle door or between his or her leg from a open position. The strategy of Baguaquan is to go to the blindside before stepping into the middle door. The single changing hand technique is a good technique to move into the middle but the opponent can still attack with the other arm or grab both arms. This is where pushing hands and wrestling techniques can be of some advantage.