Re: Kaiten nage with a bang....
Let's say you are standing at 2 swords distance from your partner.
So, one big step is enough to fully close the distance so your sword can reach him (and vice versa).
This one big step, you'd usually want to make it quick (unless you want to be stabbed) so you'd push off the back foot and either use sliding foot work like okuri ashi (very similar to how we move in aikido, only parallel feet in kendo) or you'd use stamping footwork for very quick movements.
Now you want ot cover the area super fast so you almost leap forward at your partner the right leg is lifted (slightly!!) off the ground whilst still remaining parallel to the ground. As it comes to the end of your stride your leg position has changed from nearly vertical to that of an extreme angle (left leg angled with ground right leg forward from body). This can't happen without a drop in height... drop in hara / drop in one point!
This is where the power comes from in kendo, your body.
Now, if you don't want to fall flat on your face you will need to put the right leg down and as all your weight is going forward (well at least it is for a newb like me) your right foot will impact the gound with a stomp! Provided that the whole sole of the foot makes contact with the ground simultaneously and not heel first for example.
The stomp itself is not very important... it's what causes the stomp that's important.