I've honestly found, even back when Castrum was a big deal, that if your DPS were decently geared and even halfway knew what they were doing it was often just as fast (and sometimes faster) to kill everything the good ol' fashioned way instead of trying to drag everything across the zone to within range of the cannons. The cannons are only really worth the effort when most of your DPS are fresh 50s who aren't even pushing i90 in my experience.