Define skinny for me. What effect are you looking for in with the arc tool?
Do you want the arc to be shallow.(Part of a very large circle)
Do you want the arc to be slim.(Part of an oval or very small circle)
Which effect are you looking for?
Arcs 3 and 4 are more of the effect that I am going for. The way that I've been able to do it is by bypassing the arc tool and using the curve tool. However, that involves extra steps (the addition of definition boxes to get it exactly the same on both sides).