Ive been told that most cories weill get along together and accept one another. But i would try to get two or more of the same kind and then mix differnt GROUPUS or pairs together. But i have yet to do that
I only have one kind of corys though, (pepperd same as you), and there is always the oddball of the group, he always hides and is off on his own.
So i really think it just depends on the personality of your cories.
Let me know how it goes when you add new ones because I, too, plan on adding a few panda cories along with them. My peppereds seem nice enough but right now they are the only ones in the tank.