shotgunneeley - reduce your Environment Map slider, then consider reducing the Shadow Texture Size to 512.
Both are frame rate killers.
Once that's done, you should be able to increase both your Ground and Object Detail Sliders to 4 miles, plus, you may be able to Enable most of your enhancement checkboxes.
Frame rates can vary greatly from terrain to terrain and even within the same terrain. For instance, choose ndisles and open off-line. Choose a P-51 or Bf-190a8 and go to field A-59 and spawn NE. That will give you just about the worst frame rate you will find in an MA terrain at this time. Spawn in a different directions or go to another field and compare fps.
Of course, the usual disclaimer applies, your mileage may vary.