I have encountered them on 2 occasions early in the war along the coast while flying 1/2 strutters in an RNAS squadron. I was able to shoot Boelcke's engine out once and he crashed landed, was so excited to shoot down a famous ace but even though I claimed a kill the command said I couldn't confirm it!!! Argggg...lol The one time I encountered Immelmann, we entered into a turning dogfight but he eventually broke off and headed for home at altitude, I could not catch back up with him and he got away.