At present anyone can take OpenVCE 3D Assets and other Second Life large and multi-part builds over from a BUILT version in Second Life to Opensim via Second Inventory.  The OpenVCE release box and its unpack mechanism cannot be taken over directly via that route.  It will take a few days work to restore the packaging mechanism using slightly modified scripts in Opensim.  All things we plan to do when we have time.

For now, route is:

1. Build in SL.
2. Choose one part as a core item.
3. Note or change part names (some may have component names that are not helpful) , relative locations and rotations for each part (unfortunately some may be rotated with respect to one another and at arbitrary offsets).   [Note that for the OpenVCE 3D Assets, the OpenVCE.net team we will be improving part names, removing relative rotations and adjusting the root prims to be on a very simple whole meter grid at some stage]
4. Move into Second Inventory. 
5. Transfer to Opensim.
6. Rez chosen core item and set it to a simple whole meter location with zero rotation.
7. Rez all other parts and move them to their original relative locations and rotations.