DESC: Your body grows very slowly and will take a longer time to reach your maximum size and weight. Yet you are perfectly capable of fighting and you are not considered a helpless youth.
Your growth and the bonus of population is determined by the number of class or racial levels the growth occurs over and the number of size categories your people must move through. All physical and mental abilities are adjusted per each size category as well as construction, food and water cost. All movement bonuses are also applied per size category as well. For example; a species is designed with all 100 racial levels and will have a size category of Massive. The species designer could buy this power with a starting size of small (5 levels smaller than the full size) and increase the size advancement every 10 racial levels meaning the creature will not obtain its full size until level 50.