The maximal speed phase.
The muscles of the mid-torso warrant a special mention. This part of the 100m sprint requires isometric strength of the mid-torso muscles. During the maximal speed phase, the muscles of the mid-torso must stabilize the pelvis and maintain the upper body in an upright position. The twisting action experienced by the mid-section requires explosive isometric strength endurance.
Have you ever considered including basic planks, front/back & side to improve that quality.
Performing side planks, with lateral leg raises works the glutes additionally well.
Give L-sits a go. I feel there is no more effective abdominal/hip flexor hold exercise on the planet. The position is easiest to get into from a support on parallel/dip bars.
Never let go of them stomach vacuum holds. Your working the 3 or so muscles all human movement starts from. No point having a 1000lb squat if your weak at the generator. Just won’t reach your potential.
I like the emphasis you put on the core & plyo’s (elasticity).