I've got a simple baffle (flat sheet of metal) with an offset bend (currently built as two sketch bends).  It's going in a vessel with an odd elliptical shape that will change for different sizes.  I want the baffle to be a tight fit to the vessel and I did a cavity cut on it.  

When I go back to the part (baffle) it looks correct but it gives an error when I try to get the flat pattern...  Is this possible to do?  It seems to me that the cavity would just be the same as an extruded cut on the sheet metal and that it could unbend correctly...

Let me know if this isn't possible and I will figure out another way - I could always sketch the vessel in the baffle part and extrude the cut but that seems like a lot of extra work - especially if the vessel shape changes.

Thanks