I like combinations. Last night at 10th Planet Van Nuys I taught this combination in my fundamentals class. As I have mentioned before attacking your opponents with different submission combinations is a great way to keep your opponent guessing and cause them to make a mistake. In the video below the Gracie brothers demonstrate a slick arm triangle that starts off from the mounted americana. Having played around with this while rolling I can say it is a very smooth and tight transition. One of the keys to hitting this choke is to make sure that you pin the arm down with your head. If your head is weak your opponent can easily escape the choke by moving his arm out. See you on the mats!