I like this video and explanation however why are you encouraging a semi supinated grip? Without teaching the benefits and hindrances of both pronated and semi supinated one using the latter can inherit elbow / bicep injuries unless performed 100% accurately. I know you know if someone's grip on a DL faces out, naturally, they're inclined to slightly bend their elbow as if beginning a curl on the upward movement, which can lead to tendon and elbow injuries. Not a dig, just a thought. I've used both and studied bio mechanics, A&P, and a master fitness trainer in the Army. We typically will never teach switch grip until core movements are established. And even then, under greater load, will only enforce traditional pronated.