70g sounds like huge amounts to me!!!
But I have 2 units of NR for each serve of carbs, so for me I would be having 9 units for 4.5 serves of carbs.
And for me it would also depend on the GI of that 70g.... I tend to have a little extra when having milk as I know that it effects me a little differently. It is said (on the back of my milk...lol) that 250ml is 14.8g of carbs... If I was to drink a glass of straight milk that was 250ml, I would actually count it as 2 serves because that's how my body reacts to milk.
So for me it's not necessarily the amount of carbs I consume, (I am only having about 60-80g a day) but the type. Experiment with it! Consume the same g of carbs for a few days but change the type of foods/drinks and see if your theory works!!
I have a personality, not an attitude....