Saddling up to 2 seaters was suicidal in WWI; just about all the aces agreed attacking 2 seaters was really more dangerous than dogfighting other scouts, because mobile rear-facing guns made them so lethal. Planes like the FE2b and Bristol Fighter were dangerous enemies.

My recollection is that a standard tactic was to swoop up underneath a 2 seater. That or stalk them and take them unawares.