I am using fast flow #3 with the reflux formula she normally has the newborn i find the fast flow with the reflux formula is the same drinking time as the newborn teats with normal formula i am going to try mixing 3 scoops of the reflux formula with 2 of the normal formula as they are both NAN and see how she goes because her 1st poo this morning was a lot thicker than normal like play doe where hers are normally like peanut butter (sorry for the description) and i want to avoid constipation and both formulas are 100% whey so it should upset her tummy.