I think that this is just a fantastic job of growing this clone! Incredible.
I would not be too disappointed in terms of size, I mean there are no guarantees. You just grow it to the best of your ability, the best according to what your conditions allow for. I would like to simply point out to you and remind you, are four, 7" flowers really all that bad??? Say you got a total of four, 8" flowers. What is the real difference there?! An inch per flower? Does that extra inch make them more beautiful some how?
There are just so many variables involved leading to flower size. I won't waste time going in to them at all. Just a great job of growing!!!