Copy these contents of the MEDIUM folder into the FLIGHT folder:
CLOUDinc.tga
ENVIRONMENTSYSTEM.INI
FLIGHTENGINE.INI
Options.ini and Startup.ini go into the front WOV folder.
You would be smart to x-out the old files so they are still there. That's my dumb way of backing up changes. You make Startup.ini into xStartup.ini.
If you are getting a lot of frame hits, I think there is a thread here (or 8 will drop in and tell you) that informs you which functions to turn off. We really don't want you to play without the clouds. They are Deuces best piece of wizardry, in my opinion, and make the sky look like what pilots see.