The region where to setup the zombie arena must be divided into 2 zones (parcels):
Region settings notes:
We experimented less troubles in setting the Starting parcel on a corner.
To avoid players should come out from combat zone by mistake, please build a wall all around the combat area, making it transparent if you like it most.
Do not use prims bigger than 30/40 meters while building border walls; if you make them bigger could happen that players could cross them like if they was phantom.
Walls made with prims works much better than ones made with mesh, they need less processor counts and this mean less lag. If you really hate prims, make walls in prims and set them trasparent, then put over them mesh walls and set them as phantom.
Do not build border walls too thin or players will cross them. Keep in mind that during game, players will run 4 time standard speed.