Try not to use two actions. Like when kicking, Wing Chun doesn't like to lift the knee first and then kick because this is a two step action. Also the line of force is wrong because your kick will not have ground support. Instead, your kick will transmit back to your body to off-balance you. This is why Yip Man's kick in the second set looks a bit funny at first. We want to travel in a straight line from the ground to the target, not lift the knee first.