I have printed out a deck design blueprint.It shows the deck just having a single ledger and single outer joists all the way around.I see alot of decks using double plates all around the perimeter, Is this necessary? I have a 10 x26 deck. 5 main posts across the long direction with 2- 2x10 beams supporting it at the 8 foot mark. The deck will then extend past 2 feet.