This what I get at LFSB and C130, I have not got C172: 29.6 FPS. My hardware i7 4770K default clock but turbo OC 4.2GHZ , Gigabyte GTX 1070 8GB, 32GB RAM memory. At same airport same aircraft and view I get 43FPS. So yes there is quite a large difference but the difference with your set up seems extreme. What is your CPU, memory hardware?