It sounds like it would be perfectly fine, except I would make the fish ratio more even. It's all about watching aggression issues, if any arise, and making sure there is enough territory for the demasoni, who can be little devils. My 75 gallon tank has very few "caves", unlike the classic mbuna tank, and I've never had any fish lost to aggression, or even had much aggression at all, to be honest, aside from my I very pissy female Melanochromis auratus. P. acei and L. caeruleus are very peaceful, when it comes to mbuna, so the P. demasoni may give them trouble but I've never had issues in the past so it's all up to what you decide. Just my opinion and sorry for all the commas hahaha