He tells him that the armor wouldn't fit Loras as he was too small into it, but that it fit his older brother Garlan just fine, so it was him who impersonated Renly in the Battle of Blackwater. Also, I don't remember any battle at all between Renly's assassination (when his armor is being put on
) and Blackwater in the books.
I actually like Stannis. Any more handsome and I believe the female part of the viewers would be inclined to like him, which is not
supposed to happen. I don't think the actor delivers, though. Although any more stern/less acting and I think he'd be accused of not acting at all. Wooden Stannis would have been better, though, truer to the image of the books.