Hi mkrisanne-i had read someone else did it and as long as the tins are they same brand it is fine the nan is 100% whey based so the AR and HA are almost the same except the AR is thickened so doing 50/50 makes it just right i had to go up to size 2 teats as the newborn ones were to slow with the thickened formual and on just AR she needed size 3 teats but i found it to thick so tried the 50/50 and it is working great and she is not constipated at all if anything her poo's are looser not sure if its the formula or because she had her needles and it's a side effect of the rota virus injection.
Or she could be lactose intolerant as she was on a lactose free formula before and her poo's were normal but she was bringing it all up so far the mix we have her on now is working great she is happy and sleeping great and no vomiting at all just the runny poo's that i am keeping an eye on