Thanks for your replies!
I've kept dwarf corries in even smaller tanks before (two in a 2G for 4-5 months). When I did, I did not see any signs of distress - they just acted like their larger brethren...just foraging for food almost continuously, all day long.
However, I will take your advice into consideration and make sure I do more research before I buy any.
I guess its the "schooling" part that makes the 5G too small. Clearly people have kept large individual fish. I'll keep at my search and await any other suggestions.