I have no problems at all with the yellows I have 4 big males in the same tank they have no damage at all on them theres at least 3 bigger females as well and about 12 younger ones that are unsexable (from 4 different sources), the tanks 5ft 540 litres and has a heap of other fish in it too, the general consensus ive seen on cichlid-forum is not to bother with the ratios for yellows its not as critical as with the other africans.
Im going to seperate the best male and 3 females into their own 2 1/2 ft tank when I strip the tank to get all the other fish im selling out tomorrow.. They dont seem to be getting enough food to fatten up in the community tank its a bit of a feeding frenzy at dinner time..
Heres a photo of 3 of our biggest males scrapping the smaller one was trying to join in as well nothing ever comes of it though..
Oh and good luck with the auction Steve