I would only ever house another Senegal with a Senegal. I have said it a hundred times and I will say it again; if you can afford two parrots you can afford two cages. Housing two species together in a cage is dangerous in 99% of situations, even if they are of similar sizes, even if they are friends, etc.
I may sound harsh, and I do not mean to, so I will tell you why I hold this opinion; research and experience. Research shows us that parrots are incredibly territorial animals, and that each species has unique ways of communicating, even though there are some commonalities. This means that they are programmed to defend thier territory, and also that they may not QUITE understand the signals the other bird is sending. In addition to that research also shows that hand raised parrots often lack communication skills even with their own species due to lack of natural interaction as a chick. This can lead to even more misuncpderstanding so between the parrots and. Thus violent outbursts that could even turn fatal. While I myself do not own a Senegal, there are members here that do and from what they say I understand that these birds have particularly strong and sharp beaks that can deliver very nasty bites for their size, meaning even a bird of the same size may not be able to defend himself against your senie.
Now for the experience. I got my very first bird because she tried to kill another bird that the owner brought home to share a cage with her. I have had birds lose their toes just for walking or climbing on other birds' cages. Why would you risk that?
Again, emphatically, if you can truly afford the care of two parrots, you can afford two cages. There are birds who live together, but with most species that needs to be THIER CHOICE, as in, they essentially begin refusing to live in their own cages. You forcing them is a recipe for dead birds.