Hello I am working on trying to design a wedding band to 3D print (via shapeways.com) for myself.

I am trying to design a simple curved "wishbone" style band with a simple engraving (those features can be supressed if you take a look at the model).

I am using a single loft feature with a 3D sketched spline and a rectangle sketch to create the shape. The problem I am having is that my 3D sketch is making it so that the ring "bulges" at the base because the 3D sketch is not a perfect circle when you are looking at the ring normal to the Front plane (see images below)

My question is, is it possible to make the 3D sketch Coincident with a circle (the inside profile of the ring) in the front plane?

There is likely a much easier way to design this ring and any help/advice is much appreciated.

Thank you!