Some players with less robust PC's have to keep post lighting off to have playable FPS. In some cases you can leave it on but uncheck all but anti aliasing or even uncheck that. Disabling reflections and shadows had a very positive effect of my instruments along with other things. But, with all the post lighting effects unchecked and post lighting still on, you get a better resolution of the instruments than totally disabling it. Also your video used memory can be another issue with a less robust video card running up against the max used with post lighting on. It's all about testing combinations to find some combination that gives you the best outcome for the hardware you have. In many cases a bit of time offline pushing buttons and watching the effects on your view-ability of the instruments and video memory use is all that is needed.
Also testing outcomes with 1024, 2048 and 4096 texture modes is another thing depending on your video card and PC along with different FOV. Over the two years of the alpha\beta testing program I ended up testing the game graphics against three different video cards and had to go through a lot of this to get playable outcomes with the weaker of the two.