What size is the tank? Is that the one with 36/12 base?
If that is the case, I did have a 33g tank (with 36/12 base) holding 5 x P Acei and 3 x Yellow Labs. 2 Acei males and 1 Yellow Lab male. Both species are tame and I never had aggression problems. They were all introduced as frys and reached sexual maturity and gave me lots of frys too. I believe I kept this configuration for about 2.5 years.
As Pitt mentioned, Saulosi would work, and as would Rusty (I never liked this species though). These are all super peaceful for mbunas.