It's just a single line of code. Here's the server.cs file that I use for my Trench CTF game mode:
$Pref::Server::MaxPlayers = 28;
$Pref::Server::Password = "";
$Pref::Server::Name = "Trench Wars!";
$Server::Name = $Pref::Server::Name;
//Playertype setup
PlayerMultiSlotNoJetArmor.maxStepHeight = 1.2;
//Fix ObstructRadiusDamage console spam
function WheeledVehicle::getHackPosition(%this) {}
//Disable trust invites if not admin
package GameMode_Trench_CTF
{
function serverCmdSendTrustInvite(%client, %a, %b, %c)
{
if(%client.isAdmin)
parent::serverCmdSendTrustInvite(%client, %a, %b, %c);
else
messageClient(%client, '', "Trust invitations are disallowed.");
}
};
activatePackage(GameMode_Trench_CTF);
Note the line under "Playertype setup".