Dune,
Are you running in 32 bit color?
I have the same setup, and I find that 32 bit color is good for a 10-15 frame drop in fps. Before deleting the hi-res artwork (really makes the cockpits and gauges look better) try using 16 bit color. I did and my frame rates stays in the 40's and I don't really notice a differance in the appearance of the sim.
Sharky
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Playboy Leader
307th FS/31st FG
You can run but ya just die tired