You missunderstand Cirvol.
All your systems need to have connection via warppoints to an open system (or to a system connected to a system connected.....to the open system). If you have system shields (or using the 10 warppoint rule) this will mean that everybody who wants to attack you beyond the open system has to attack through a warpoint giving you as the defender all the advantages.
Beware though; when the fleets get really huge, the advantage to the defender become less
