It would be helpful when referring to carb limits on this global, diverse forum to clarify “my max carbs” or “induction period” or “IR max carbs” etc. I often see some commentators referring to max 20 grams as if it is a monolithic rule - a generally accepted part of the ketogenic way of life for all - which it most certainly is not.
Nor is it substantiated by cornerstone LCHF/keto researchers the Drs. Eades, Stephen Phinney MD, Jeff Volek, and Dr. Atkins when pertaining to the non-insulin resistant or to the IR folks who’ve done years of keto recomposition and are able to proceed to “dietary recomposition maintenance” level then “lifelong maintenance level”. Nor does it apply to fat-adapted endurance athletes, who may do quite well on 150-200 grams of carbs based on a 5000 cal. intake of fat and keto foods.
To clarify: not disagreeing that the “induction period” of the first 2 weeks of keto is an “Under 20 Grams Carbs” proposition in order to get largely fat-adapted. This is what the LCHF/keto physicians I’m familiar with all advise. Atkins is net 20 grams Phinney & Volek is total 50 or less (25 grams or less net) and the Drs. Eades are 30grams net. Even that is a 20-30 range.
HOWEVER - after two weeks of initial fat-adaptation improvements, the Atkins Phase II, and the Phinney & Volek as well as Eades guidelines long term allow going up 5 grams daily carbs per week until one finds one’s ‘sweet spot’. Atkins up to 50 grams net (100grams total) for the Atkins Phase II. For Phinney & Volek 75 grams total or more, Drs. Eades 100 grams net or more - depending on health profile, etc. Then there’s Atkins further phases (Phase III and IV) with even more incremental carb testings and levels. Phinney & Volek point out that for certain metabolically healthy people, up to 150 total or more can work - and Dr. Fung focuses on the radical nature of small eating window and fasting more than actual carb amounts, etc. Last but not least, there’s general n=1 lazy keto, which may vary weekly and include fasting or not.
We all know that this wonderful forum has a diverse range of health profiles and hormonal statuses - that being said, there is no Max Carbs = 20 rule carved in stone for everyone.
The extremely insulin resistant (metabolically deranged and morbidly obese, esp when combined for a long time ) do well at less than 20 grams for YEARS or a whole lifetime for body recomposition and regeneration - this is true.
The non-IR and even pre-diabetic folks can have massive health improvements in the first 6 weeks of keto that reverse their health profile to “non-prediabetic” and confirm them as “metabolically flexible”- whereby body recomposition can percolate great along at 50-75 grams total carbs or even more.
My personal intake of carbs ranges varies, and is often 50 net per day, and I drink red wine a couple nights a week with certain foods. I feel GREAT and my body recomposition is progressing season after season.
I suggest aiming for precision language when writing about carb limits, framing context as personal or in reference to specific keto physicians and their recommendations - and not prescribing one’s personal prolonged induction period/-20 grams on all others as if it represents some universal keto rule, which it does not. 
Otherwise, there are nuances that get lost, and that’s a cryin’ shame.
Ab crunches though are now considered largely useless, (and can cause or exacerbate diastasis recti), so they can be ignored.