Not bad 6/10, i prefer small sigs "height wise" yours are really tall.

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When you do the render layer, press, "CTRL+T" this opens Transform: make it fit the size of ur sig, Remember though that when your changing the size that when your down size a render the quality of the image stays but when u Upsize it, it becomes blurry.
Now, once you've shaped it, it may look crap however once u apply it! All the rough edges go away.
I find its best to fit a render to you sig size than the other way around.