Too many drakes

[KikiDeAnime]

Found out that Colonel's offspring that I kept from Kaeda's egg has turned out to be a boy. Unfortunately I only have 5 females. 4 of them are currently with our 2 breeding males free ranging 24/7.
Colonel, Beaker(His son), and a female I got recently live with the chickens for now as I need to finish putting hardware cloth around the chicken & duck yard to make them secure. Both father and son get along nicely as I will sometimes spot Beaker resting beside him.

As of right now Colonel doesn't attack Beaker but I know that once Beaker is sexually mature, they will start fighting.
I don't plan to rehome any of the drakes.

I just have 1 question.
If I decide to keep Colonel and Beaker in the same yard together with minimum fighting, how many females should I add?

If I'm unable to keep them together, I can always keep either Colonel or Beaker with the chickens along with 2 female ducks.

 

[The Birb King]

Male ducks and chickens should not be kept together drakes can mate with chickens and that can kill the chickens

 

[KikiDeAnime]

Male ducks and chickens should not be kept together drakes can mate with chickens and that can kill the chickens

Colonel has lived the chickens for 4 years. I wouldn't keep him in there if he was a danger to them

 

[Isadora]

Typical rule of thumb is 4-6 females per drake.