During total war, how can one select an alliance much stronger than they?

On the declaration page, at the bottom there is an option to use stones to find an opponent. This opponent will be random so you have to spend stones again & again until you get the opponent you want. Each time you press the button it cost you 10k stones so think before you start spamming it, also, the alliances that are in a lot higher rank than you are there for a reason. Make sure you do not pick an unfavorable match up.