Troubleshooting the Front Kick if you can't seem to balance correctly upon impact
Face off with the kick shield and kick it with a regular front kick. Most often you'll find if you're off the target you've got a tendency to spin and the target wobbles. You'll find the support leg experiencing a lot of torque-ing forces.
I've noticed that this happens especially for the Do-san back leg front kick because many people pull the knee up straight towards the target and then fire off the kick. This means that, if you draw a line from the back foot to the target, it comes up a little away from the supporting leg.
Troubleshooting this, you can raise the knee and apply inside tension using the inner thigh muscles - this draws the striking knee closer to the support leg. Any front kicking action then is applied from closer to the COG and centreline - in fact the whole body shifts closer to the support leg. This reduces spinning forces on the rebound, and allows you to strike with better hip power.