Doing a second test, matching criteria laid out I tried a few flights at 5 -10,000 feet higher than a 109. Even knowing it was heading towards me but off to the right I couldn't spot it on any of my 3 tests.
This hasn't turned me from fan boy to skeptic since I think finding one lone plane at different altitude and unknown location isn't going to be easy.
However I certainly agree that having options like model enlargement are a good thing. I think one thing that could help would be seeing a glimmer or reflection on a plane. I would think IRL that would be something you would see.