Using Zone Manager, I created a zone which has the following properties:
 
{
      "Name": "island",
      "Radius": 150.0,
      "Radiation": 0.0,
      "Comfort": 0.0,
      "Temperature": 0.0,
      "SafeZone": false,
      "Location": "-1599.588 0.4348569 -1551.852",
      "Size": "0 0 0",
      "Rotation": "0 0 0",
      "Id": "91948830",
      "ParentID": null,
      "EnterMessage": "You are now on PvP Island where players and buildings take damage \nYou cannot teleport out, you must find a boat, swim or fly away",
      "LeaveMessage": "You are leaving the PvP Island",
      "Permission": null,
      "EjectSpawns": null,
      "Enabled": true,
      "Flags": "AutoLights, NoBuild, NoTp, EjectSleepers"
    }
	I use the default ruleset so I created a second one where Default Damage is true and the zone above is selected. 
 
	I can't seem to do damage
 
	 
 
	Based on this ticket, I changed the rule name to exclude and it didn't do anything https://codefling.com/files/support/3610-set-pvp-zones/