Can you post the model here?
You can use Offset Surfaces to Cut with Surface your nest part. The trick is that the surfaces have to be hold water, just like you were making a solid, so you may have problems with the imported surfaces, depending on where the gaps are.
ah figured out a work around with the surfaces issue, i imported to autodesk, simplified the part and then saved out as a x_t, did a lot of healing and it works. However because its hollow it didnt work how I wanted it to,will try the cut with surfaces.
Dan can you post your part or even show a snaphot of what your working on?