Well presumably rounding up support locally whilst still trying to stay undetected is pretty hard. Realistically you'd probably only want to have enough people

Well presumably rounding up support locally whilst still trying to stay undetected is pretty hard. Realistically you'd probably only want to have enough people for the plan to succeed informed, any more and the chance of detection rises. As it was, the U.S. tipped them off anyway and they were waiting for them, so they probably would have needed a lot of people to succeed.