Which knuckles should we hit with? Front 2 or back 3?

https://www.iainabernethy.co.uk/ A short video on whether it is better to hit with the front two knuckles or the back three. NOTE: To illustrate some general points I hold my own fist against the side of my skull when talking (rest of body not in shot and holding my fist against my jaw made talking awkward); this in NO WAY is suggesting that part of the head is a desirable target (although it could be accidentally hit in the chaos of combat). The video also briefly discusses the merits of closed-hand striking vs open-hand striking. I hope you find my take on these issues interesting. All the best, Iain