I did add it in the defaultgame.ini file but it didn't work.
I did manage to get it working (after some sleep 61 hours in already) by adding it to the server.json file, under the additional settings.
"OverrideShooterGameModeDefaultGameIni": {
"NoClaimFlagDecayPeriodMultiplier": "4",
"PlayerDefaultNoDiscoveriesMaxLevelUps": "255",
"bClampHomeServerXP": "0",
"bDisableStructurePlacementCollision": "true",
"ClampHomeServerXPLevel": "255"
*Note the server.json file has a setting to override the game.ini file: "OverrideShooterGameModeDefaultGameIni": {},
Thanks for the input and suggestion.