Right. how about placing a static aircraft of the opposite colour to your searchlights inside a house or something? Might work. That or set your lights to the opposite of the payer aircraft. That'll light things up,
Light 4 IIRC is extra bright but the lights don't illuminate. You can brighten lights by, once placed, pressing "Insert". A second light will appear very close to the original and, if already elevated, at the same height. Also by pressing "Insert" after placing any object will give you a duplicate.
About the only "light" that illuminates is the "Airfield Campfire". I have used that, placed close to a closed hanger door to simulate late night welding.