I think the brown on the undersides isn't quite right, still. It's too prominent, and too bright. When you see a car with a fan of mud spraying backwards from the wheel well (like it was flinging mud for a while) it isn't very bright. It gets dull as it dries on. I think maybe a number of things might help, such as reducing the opacity on your current level by half, or changing the hue/saturation of that layer, or something.
Ink, one valuable tip is when you think you are done, don't just get ready to hang up your tools and submit it. Rather, when you think you are done, save it and sit on it. Don't even LOOK at it for a week. Forget about it as much as you can. Then in one week open it up, look at it in-game and in the skins viewer. You get a set of fresh eyes on your progress that way. THEN, do the changes that will pop out at you (i.e. forgetting landing lights or some such), let sit again. When you get to the point you notice nothing missing and nothing overlooked, submit it.