Front arm backfist in with boxing punches?

Ok we often see the spinning backfist.

But we rarely see the backfist with the front arm.

Im not talking about the speedy backfist used in some martial arts, im talking about the more powerful but slower backfist which I belive was used in old school boxing.

I believe they used it after throwing a left hook, instead of coming back with a right cross, they would sneak in a powerful left backfist instead.

Is this a viable and useful technique in kickboxing?

Why isnt it used?

How would you use it?

Any way try throwing a left hook freeze once you have finished the left hook so you are at the end position, now instead of coming back with a right cross, torque your hips like with a right cross and smash them with a stiff armed left back fist.

Its a bit like the x2 elbow used in muay thai left and right with the same arm.