if you are able to get a larger cage then get one. the bigger the cage the better. but as for lessening the aggression in dominance fighting in male or female rats with getting the larger cage, solong as the first cage isn't too small to begin with then the larger cage isn't going to make a difference. and both males and females will fight about the same. adolescentence does increase the desire the assert the dominance and struggles within the heirachy does arise more often during this time but its no different between males or females. and for the most part a fight here and there isn't that big a deal anyway, everyone has agruements with their roomates afterall.