We were not able to do 80% EN without doing feeds at school. My daughter was on 85% formula, 15% food and we had to do feeds for 18-20 hours a day.
But I'm guessing your girls' feeds run at much higher rates, which is how you do it all at night?
M was getting 100 mL/hr, but into a NJ tube. It bypassed her stomach but she wasn't hungry. But she was getting calories all day, so that helped. And she was allowed to eat a little at school.
At the time, she had been so malnourished for so long and was so unused to eating, she didn't even seem to remember what hunger felt like. We quickly figured out that she would get cranky and upset when she was hungry or she'd find it difficult to concentrate or get a headache.
Her stomach was just so unused to food, she didn't feel normal hunger.