Good description Qwerty, the only other thing I can add is when the kick ends e.g hits the target, your front foot left in this case, should be facing almost behind you as pivot left on the ball of your foot and turn your hips in same direction, this should be 1 fluid motion through the target, instead of hitting it and pulling away when you do so. As your quite a big fella you should be able to do some good damage when you learn the right technique.
The only other thing is you'll know when it's about right as you'll notice more of a quiet thud more than a loud slap when the kick hits the pads.
Good examples are Buakaw por pramuk, Gilbert Yvel, Mirko Cro Cop to name a few.