I would think a marker the size of a credit card standing longways up would be the max size. It would be much easier to aim with a camera next to the gun. Shenloco once proposed two camera per tank, one guy to drive and the other to shoot, like a real tank crew! I think it would be great, the only downside is that we're all too far apart to get enough people together. In order to go 3 on 3 or 4 on 4 you'd need 12-16 people!