Variable thickness, on an archtop Guitar, impossible?

Hi All,

I was wondering if any of the experts here can shed some light to this problem...might be easy to do, but for the life of me, I do not seem to know of a way to do it in SW2011...

I have attached a pic of the model I am building:  It is that of an archtop guitar, which as you can see, I have modeled the top surface.  I did this using cycloid curves which I calculated, and then building the mesh, which allowed me to create the surface.  So far I am pretty happy with the way it looks, although it needs minor tweeks....now here is where it gets interesting:

I want to create a solid for maching BOTH the top and the bottom, but the thickness of the top varies down it's length...for example, the thichkness at the center is about 1/4 inch, then it goes to 3/16 and then down to about 1/8 as you approach the edges...

How can I thicknen this surface, or what tricks can I use, to achieve this?  Obviously I want the part to follow the surface from the inside....any ideas on tools or a method?  I am thinking something with a sweep, but it beats me how to achieve this....

Thank you all for any suggestions or ideas!

SolidworksParts And Features