Do your build as a pistol first so you can blast away while you wait for your stamp. When the stamp comes, slide the stock onto the tube and you are good to go. This is what I have done.
I've seen some guys talking about doing this...it would deffinitely make the wait easier for the stamp!
One other NFA question I had, and I guess I can hijack my own thread; I understand that Class III guns need to have the owner's name/trust/corp. engraved on the registered item. Does this hold true of suppressors too? I'd like to get a KAC NT4 in the near future, and I can't tell from the the heat shield where I would have my engraving. Then again, none of the pictures I've seen of privately owned cans show anything like that.
Thanks again everyone for the advice.