Hi Java. Don't know if you had much time to review my research in the post that I made on fixing sprinter's posture (link), but I document in detail about the performance disability that DD, myself, and countless others have, quad dominance.Jryan,
You were very much in my thoughts (well, B was...) when I put this together.
And although I love your illustration above... some kids (and I know you know this better than most) simply cannot overcome the negative position of the hips... in relation to the knee & shoulders. As such, we can displace the hips initially... a la STFG... thus allowing them to utilize a better positioned posterior chain earlier in the motion.
I'd be curious (even if it were offline), if B gave this a go? Hope you are all well, and say hi to her for me!
Quad dominant kids just cannot produce thrust from the middle regardless of their efforts (trust me, we tried for a very long time). It is a wall that cannot be scaled without resolving the underlying issue which is in their feet and specifically with the arch. I don't have a bullet proof solution yet other than for everyone to 1. recognize it, 2. work to strengthen the foot arch, 3. keep high focus on foot strength during strength and conditioning workouts
I will make a bold assertion... Every high level pitcher has thrust from the middle regardless of how much they bend at the waist.
There may be rare exceptions, but not enough to forgo saying that "thrust from the hips is an absolute".