I work in a sign making shop and up to this point we've only done 2D designs. We have a customer that wants a 3D design of a coffee cup, and we can't figure out how to make the cup essentially a half dome. It should be 1" thick in the middle of what would be the rim and be about 1/4" thick around the sides and bottom of the cup. So far we can only get it to be a dome where the high point is in the middle of the cup and thinner around the entire outline.

Any advice?