Folks,
If your frame rate remains satisfying, try changing these two parameters in DATA.cld:
BASE_R_DISP from 6 to 4 (makes clouds somewhat smaller)
DENSITY (in both levels) from 1 to 4 (increases cloud count)
The result will be max cloud top height equal to the high cloud layer (about 24,000 feet), and nearly overcast coverage in thunder. A potentially viable alternative If you'd like to get on top of the clouds sooner/more easily.
I tried changing density to 8, but the game locked up and within seconds created a log.lst that was 6Mb in size!
I have no idea if this is at all the case, but my pea brain tells me that DENSITY *may* be quantized to factors of 2. I'm not sufficiently motivated to explore the gamut, as on my machine a value of 1 is as high as I can go if I want to preserve every frame I can, because my head tracker rate halves suddenly if FPS goes below ~55. I want to avoid that if at all possible.
I mention this to also inspire y'all to not be necessarily satisfied with another's take on things. Wade in there and tweak to your satisfaction.
And you could create an extra version or two of DATA.cld, choosing which to activate before firing up the sim. Such an approach to 'custom' clouds could be useful for different theaters and seasons. A northern winter campaign will not typically see cumulus build-ups anywhere near summertime or tropical extents.