But it does have some problems. In order to work there are some requirements. Other than knowing the technique, you must have sensitivity to the opponent's energy. Or you must have an opponent whose energy is not centered. Actually you have very little chance of running into someone with very good centered energy, so you are in luck.
Attacker wins with lop sao and backfist.
In figure 5, your luck has run out. The person who blocked has very good centered energy. So you punched. You grab his blocking arm in order to Lop Sao and, much to your amazement, both of your arms are Trapped and he is pounding a hole through your chest. Look again at Figure 3.