Q - How long does it take for the shutter to close once the button is pressed?
A - For the shutter arm to move 180 degrees takes about 2 seconds, if you set up the shutter so it only requires a 45 degree movement to block and unblock the lens the time would be about 0.5 seconds.
Q - Can the remote controller and the “at projector” be in operation at the same time?
A - Yes, both switches can be operated at the same time with no damage, however if the remote switch is in the "close" position the "at projector" switch is operated nothing will happen, so if your trying to adjust the arm position besure to leave the remote switch in the "open" posistion.
Q - How big is the dowsing flap?
A - The dowsing flap is the circular part of the shutter arm that blocks the light from the lens and it is 4.5" diameter.