Growing Australorps to eat

[AustraHatch]

Hey guys, im raising 5 black australorps and 5 splash australorps. i have 2 excess roosters (1 splash and 1 black). They are currently 13 weeks so obviously not ready to eat yet. But i know that roosters mature much earlier than hens and was wondering at what age should i harvest them?
They are currently a maybe an inch taller than my isa browns

 

[kattabelly]

Depends. Do you want them to reach a certain weight? To be able to cook them a certain way? (Some people will advise cooking a bird low and slow if it's anything over 16 weeks; personally I'm happy roasting birds a fair bit older) Is flock harmony more of a priority, if you aren't able to let them range over a large area or keep the boys separately once their hormones start kicking in?