My thinking on situations like this one vary from most. There are times when it is an advantage to the player needing only one ball to position both balls down table. But if you elect to do this, you must be certain not to leave a shot. This unorthodox move will win you the first shot a high percentage of the time, and lets not undervalue the strength of the first shot. I have opted to do this many times and definetly have benefited from this, so called gutsy decision.
In this situation if I were to reposition the 11 ball down table I would be mindfull of not leaving the return billiard off the 5 ball. I would hit this shot with the speed to go 5 rails, with enough speed to bounce off the 5th. rail 5 to 10 inches.
I'm not opposed to putting both balls down table if it is going to win me the first shot, or put my opponent in trouble. That also was my way of thinking when there are 2 balls on the foot spot with the shooter needing only one ball with ball in hand behind the head string. I play both balls, opposed to playing conservatively. Right Doc? Of course I practice that shot and hit it well a high % of the time, which is imperative.