In Arma 2 the harrier had some really good markings on the topside of the canopy. As someone who plays with headtracking i currently find it easy to get a little disoriented when flying the 'wipeout' and looking in upward angles for example.
I think it would be nice to have some sort of markings on the top of the canopy to easier keep track of how the plane is oriented without having to look forward to re-assess your orientation.