I don't know what screen setting you are using Slasher, but I have just about doubled my frame rate in MS Combat Flight Simulator and Jane's WW2 Fighters by changing down from 1024 x 768 to 800 x 600. I'm running an AMD K6 450 with 64MB of RAM and a Viper 550 graphics card with 16MB of memory.
Don't forget to modify your Combatfs.cfg file if you do change.