FPS hit in later stages of Hammer Campaign

[psylent]

My FPS are fine in regular missions and the early stages of the Hammer campaign. They would be in the realm of 35-40 FPS up to 70's in some instances. (All Settings Medium)

 

But once I started about stage 5 in the campaign, the FPS started dropping. The worst came in stage 6 where my FPS is around 17 and down to 8 once airborne making it unplayable.

 

This is with all settings Medium, shadows off, cockpit 512, water low, no civ traffic and all bells and whistles off.

 

My system:

 

AMD Phenom II X4 955 at 3.62GHz

8.00 GB RAM

Win 7 64 Ultimate

GeForce GTX 460 1GB V-RAM

 

Plays fine maxed out in training missions, other regular missions, and the first couple stages of the campaign.

 

Any advice would be greatly appreciated.

 

Psy

[psylent]

Update:

 

Selecting the Auto Low option and changing cockpit to 256 gives me 25-30 FPS on the tarmac and then airborn 35-40 FPS. Preload Distance to MAX, and no birds, clutter.