You can try to lower resolution of SC assets, but with such detailed geometry of assets, I'm afraid it's not going to help much, but maybe it can make difference between playable and unplayable.
There are like 2 dozen highly detailed and animated human models onboard, and dozen of static F-18 (each one with same poly count and texture as your own F-18 ). And I will not even mention F-14 model. Massive performance hit was reasonable expectation.
Things you can do:
-Open every mission, delete static crew, change static aircraft to old F-18C, or even older F-18A, delete thugs, cranes...
-Open SC asset textures and reduce resolution. (Someone will probably make a mod for that eventually)