I've got a large parkade with five revit files (buildings above) linked into it. I'd like to have my elevator and stair core walls drawn in the parkade match the elevator and stair cores in the building above (I might change the location of the cores at some point in the future, and would prefer if the parkade cores could match the adjustments).

The reason I want seperate core files is the buildings are very large files. With five of them loaded into the parkade file, revit really starts to slow down.

I thought it'd be simple. I drew core walls in the parkade, and locked all four walls to the four core walls in the linked building above. To test that it'd work, I opened up the linked building file, and stretched the core to be 30m wide. When I updated the link in the parkade file, I expected the parkade core walls to extend out 30m. Instead, I got a "constraints not met" error, and the linked file itself moved 30m (leaving the parkade core untouched).
I'm kind of surprised it worked this way. Is there a way to tell revit which of the constrained objects is the host, and which is the slave (for lack of a better term)?