Super Soaker Central

My brother and I are planning a major water war. And we can't decide on a standard to follow for when one of us is "out". So far we have this is the idea: when most of the shirt is soaked, you are "out". Is there a more precise way of knowing when someone is "out"?

The way the Ridgewood Militia and WaterBridge determine is if there is a spot of water on your shirt the size of your fist. Also, we try to have an honor system, and it works.