Sorry I can't help you, other than to diss sit-ups in entirety. The damage they do the spine is enormous, and they're not exactly functional unless you are a very weak person to start with. If I try to do sit-ups, I get a nauseating scraping POP each rep, somewhere around L2 or L3, and if I don't stop, it gets swollen and hurts for up to a week. That's a cartilage/soft tissue injury. I'm just lucky it out-and-out hurts me, unlike many others who simply accumulate damage for decades only to accrue scar tissue and damage.
I do hanging L-sits, leg lifts, backwards leg lift with gentle spine flexion, lots of good core work, but not with pressure on the spine.
Steak, eggs, potatoes - fruits, nuts, berries and forage. Coconut milk and potent herbs and spices. Tea instead of coffee now and teeny amounts of kelp daily. Let's see how this does! Not really had dairy much, and gut seems better for it.