I have found an application for oi-zuki. We call that the "front punch" but the actual translation is "pursuing punch." It is very powerful, with all that body weight behind it, but it is also very slow. Trying to find a practical application for it isn't easy.
It just popped into my head. I guess the famous tengu have come visiting again.
Imagine yourself beset by a mob. You're dealing with the guy in front of you, and you neutralize him. Your immediate response is to mawate (turn to the rear) for a reverse punch at the guy behind you... but he is a little out of reach. You instantly take the reverse punch and turn it into a front punch by stepping toward the enemy. Pursue him!
Oi zuki is the second stage of the reverse punch. I'm going to start teaching it that way.