Double-shelled undulating surface

Hi all,

I'm trying to create a completely parametric double-shelled light enclosure that will then be contoured and laser cut out of clear plexi. The exterior shell will be smooth and the interior shell will be "wavy" and ideally will respond a bit to the demands of the space. Now, its been easy enough for me to figure out how to get the shape of the exterior shell and I've been able to get an undulating surface in the xy plane using attractors. The trouble I'm having is combining the two concepts to produce the interior shell and tying it all together parametrically. Attached is the current definition I'm working with and the rhino file. In it you can see an earlier(uglier) and un-contoured version of what I'm attempting to create - its easy enough to do in rhino using lofts but it would be great to get the whole thing running in grasshopper.

I know this is asking a lot but any little suggestion will help, I feel like I've exhausted most of the options I know of at this point. 

Thanks