I have a BO and they are large birds and like others mentioned you will need additional room inside for roost space and for them to get around. I found on this site more than 75% of the posters say they needed more room than they expected. You will have way less issues with more space.
Thx for the replies everyone the chicks are here and are about six days old now. they are growing very fast and seem to be doing fine there all being active.