Should a group of 5 have an ameer?

Answer

A group or a shura group may be any number of persons. It is not restricted to 5 or 3 or 10. However, regardless of the number of the shura, there should be an Ameer. The Ameer has the final say to accept or reject the advice of the shura. The shura does not have the right to impose its shura/advice on the Ameer.

The Sunnah of Shura requires the Ameer to consult with the Shura members or with outsiders, then he should reflect and ponder on the different advices given to him. But in the final analysis it is only his decision. There is no such thing as majority opinion in Islam.