If you're only pushing a cc or two, I would just go with it, I think you'll be fine (assuming you don't have a lot of fat on your ass). I would however try to rotate and hit 1" in the glute as little as possible just in case.
I have always used 1.5 but Needsize was saying in a post just the other day that all he ever uses is 1". Unless you are a total fat ass 1" pins should be fine for glutes.