I don't keep either species, but in general mixing is frowned upon for potential toxicity reasons (and other problems). Specifically, I've read several times that Cubans are high on the toxic list and definitely shouldn't be mixed with other species (also, they will happily eat any other frog they can get down their gob).
So yea, I'd look into that very carefully and hopefully members more experienced with Cubans can chime in here.