My severum is a very, very timid fish and about 2 inches long. So far (3 months) he's never shown any interest in the other fish. As far as the cory's are concerned, interacting with the spotted's has never been an issue and I've had the largest of the two for years... about 4 now. Maybe I just own two very strange spotted raphael's, but they keep to themselves (coming out for food, grabbing a pellet and not coming out again until the next night) and just swim further into their driftwood cave should the cory's school near them. My cory's are full grown at 2 to 2.5 inches and very tall. They're punctatus if you're at all familiar with that particular cory. Maybe they just intimidate the spotted's being that they school so often?
MetalHead, how big was your girl's upside down? Mine is a decent-sized little guy who lives in a particular scoop area of my centerpiece driftwood. I've seen fullgrown severum's in stores and the shape of their mouths doesn't look at all like they could handle my little guy.