if you get a breeder style tank then i would see no issue with a pair..
if you get a standard size style tank then with the pleco probably no issue.. they'll only eat what can fit in the mouth.. so get him small (you can keep large schooling fish) and allow them to grow up together.. as he is larger the tetras etc will be at full size and you shouldn't have issues with him going after them as they are already knowing whats what in the tank compared to having a fully grown one and throwing in the tetras.. nice treat lol