What works for one flock may be completely different from what works for another flock... sounds like you have a good handle on integrating already, you know to observe and watch for issues... if any happen, simply separate and wait longer...
I have multiple drakes and multiple ducks... many actually *do* pair up and go their own way... especially if you can free range them, this can work out just fine... just be prepared in case the boys get overly agressive to separate them into their own area for a while and you should be just fine...