You can't really set OPTI mode. If you have VPS enabled it will come on if it can't get a GPS lock and has enough light and contrasting items on the ground to key off. If it drops into ATTI mode the aircraft will drift without stick inputs to counteract any movements.....meaning you have to actively fly it to keep it's position in space. In ATTI mode the aircraft acts like a puck on an air hockey table where it can effectively slide in any horizontal direction. In smaller rooms your going to get swirling air currents coming off the floor and walls which will