whilst small you may get away with a pair of dovii, but much past 8" the male will probably kill the female and any other tank mates. An adult male is an impressive site and will make the female look tiny in comparison.
I have always wanted to set up a huge tank with plenty of rocks and cover and introduce say 20 convicts male and female. let them breed for a year. the introduce a pair of 5-6 inch dovvi and see if they would coexist.. yeah i can dream and have no space left for another tank.