I need a tip for a future indoor flight in a large gallery hall which will be shielded from any GPS or other electronic signal for that matter. If the Phantom 2 is run in GPS mode but with no GPS signal, how is its response to control inputs? I realize it won't likely hold its position in GPS mode and I'll have to keep an eagle eye on it controlling it foot by foot. Its a large gallery with plenty of room. Any tips or suggestions?