I think that Mitchell is an exception. The reason most people say stay clear of clams until tank has been up for 6 months is because the aquarist themselves are new too. The first posts I seen from you was your build thread and you looked new to the hobby. Well new people tend to mess up, but the cool thing is, you are vigulant and a dedicated saltwater marine keeper, and you are the exception. I think you're right too, Bigjohnwoody will be good because he is not new and will be able to do the things you did in order to keep a successful growing clam this small.
BTW, Big John, that clam is hot!