Cardboard buck

Hello everybody I want to build a cardboard buck to full scale of a Ferrari 458 italia dashboard. I have found .obj and .3ds files of full car an can open in rhino an delete away everything but dashboard. Thing is the dashboard well whole file is in mesh forum an back side of dash is all open so when I do contour lines command the lines come out funny or not even connected? Now if I could block in back of dash that would be fine but it’s mesh an a pain in the butt any pointers or just point me in the right direction would be awesome thank u all for your time

Without seeing the file this is a guess but could the OffsetMesh command with the Solid option help? You may have the best luck doing this on the larger portions only.