Hi Sydney,
Macro even of a butterfly on a pin in a collection is a challenge as Fahim as indicated: narrow depth of field. The idea of this lens as close distance with a living cat, is one that most folk wouldn't attempt. However, with the same lens at 6 feet you are already doing better. This happens to be a great lens and you have enough pixels to spare. I'd close down the aperture to f 8 and see what you get. Also you can post this at say 600 pixels wide so it does not require a lot of bandwidth. Unless you have some fine detail you need to show.
Asher