i will find you a pic where people have used fire brick in round ones before. and it will help keep your bottom from rotting out.
as far as heat flow, its more maintaing the heat so you do not have to mess with your fire as much. the coals will burn longer etc......
as far as heat flow, its more maintaing the heat so you do not have to mess with your fire as much. the coals will burn longer etc......