I just ran a couple sessions of the ol' Sunless Citadel, and honestly hardly modified any stats at all (primarily rats, kobolds, and goblins, not to mention the water mephit that they simply ran from')
I normalized skill checks to either 10 or 15, depending on difficulty, and kept the same hit points and attack mods for monsters.
Whether I was accurate or not, in the end, didn't seem to matter. It was just the right amount of difficulty, and everyone had fun.
So... Success!