here is 4x24 with much less flexion in the spine. was aiming for shoulder blades just off the floor.
I think I found a weak link in the chain and a answer to all of my issues with being stuck on this. the last set of 4x24s was actually surprisingly tough and felt my lower abs really begin to fatigue in the final seconds. I am going to hang out at 4x24s until a period of underload is achieved.