I was once in a attempt to have the world's biggest orchestra. We ended up with only about 2500 players, but the players were so far apart that there was up to a third of a second delay in the sound from one side to the other. We did have a large screen in front showing the conductor, so we simply ignored the sounds we could hear (especially the trumpets who always play as loud as they can) and follwed the conductor exactly. God knows what it sounded like from afar. What I would recommend in such attempts is to stand as close together as possible. Being string players we are used to sitting on chairs, but that takes too much space. The cellos however may have chairs.