Have you managed to have a hit yet?
Not sure if this was a product of the "early prep" we've been working on, but I was hitting like the white shirt guy on the weekend. Maybe the problem was I was so focused on early prep, I wasn't focused on getting my arm off my body and creating at least a 90 degree angle between my forearm and bicep (it was probably more like 45 degrees in the take back, leading to white shirt guy type forehands). This will be my next focus... early prep + getting my arm/racquet back further enough.
It didn't hurt my wrist at all. I can get a sore wrist if i'm too stiff or forget to shoulder turn, though.
I might also try a similar concept on my OHBH - maybe even the straight arm backhand. I've tried it before trying to imitate Thiem, and it packs a punch. But it was harder to pull off... but maybe not as hard with the early prep.
Also, early prep is one thing the white shirt guy has going for him. You can even see it in the thumbnail for the video. He runs to the ball while prepped like Nishikori and Andrei. The only thing though, is that he doesn't then 'throw the racquet back' (like skimming a rock) that @Pete Player was referring to. It seems like this is the ONLY reason why his forehand lacks power. I'd like to know if anyone disagrees, and why.
The white shirt guy actually won this match despite having such a pushy forehand. I think because he was very alert with his early prep - he just was able to react to so many well struck balls from the black shirt guy. The black shirt guy seems like he could do with some more early prep focus to improve his consistency. Its probably funner to play like the black shirt guy though, lol.
It was such an interesting video for me, because they're both doing some things right but have completely different results.