This play is a very close call. It is so close that the stragedy for this particular play changes if you are using 1 deck or 6 decks. The stragedy for 1 deck is to double and the stragedy for 6 decks is to hit. You should double if your true count is plus 1 or higher with an 11 vs an Ace and hit on zero or negative counts. If you don't have any idea what the count just double when playing with 1 deck and hit when playing with more than 1 deck.