Best "A" seat for legroom (if 19A isn't available) is 2A. Lift the arm rest (by pressing on the small button underneath the arm rest toward the back) and sit diagonally. Your legs will stretch right into the galley. Obviously, this only works when the FA isn't in the galley or moving to/from the jump seat. On one of the longer (2+ hour flights), the FA may only go through the cabin 1 or 2 more times after the drinks service, so that will give you plenty of time to stretch out.