The Buffalo Heads will pair up as you have described. There is a good article on them here.
http://www.cichlid-forum.com/articles/s_casuarius.php
The Ps. acei are not pair bonding fish, and are best in groups with a male and several females. These are mouth brooders, and sometimes you will get conflicts between mouthbrooders and egglayers (such as the buffalo heads). The egg layers will try to defend their fry, and the mouthbrooders will try to eat them, so there would be some conflict.
I don't think it would be an impossible mix, but eventually the fry will all get eaten.
Do you know the water parameters of your aquarium? The ph?
http://www.cichlid-forum.com/articles/s_casuarius.php
The Ps. acei are not pair bonding fish, and are best in groups with a male and several females. These are mouth brooders, and sometimes you will get conflicts between mouthbrooders and egglayers (such as the buffalo heads). The egg layers will try to defend their fry, and the mouthbrooders will try to eat them, so there would be some conflict.
I don't think it would be an impossible mix, but eventually the fry will all get eaten.
Do you know the water parameters of your aquarium? The ph?