This might better appear in a more appropriate sub-forum where I cannot seem to post...
I run v4.08, and have just come up with a way to enjoy a custom high cloud texture for each mission in static campaigns.
In the map's folder where its load.ini resides, I create a new load.ini for each and every sky I use. The only difference among them is the highclouds and highcloudsnoise entries, which load the relevant textures residing in the mapmods/maps/_tex folder.
Then for each .mis file in the campaign I direct to the appropriate load.ini.
For example, one might have textures (in the _tex folder) for scattered, broken and overcast cirrus. In the map folder one might create, e.g.,
load_sct_ci.ini
load_bkn_ci.ini
load_ovc_ci.ini,
the only differences being the high clouds and noise entries for the loading of the desired sky textures.
I just did this for the 26-mission Cactus Diary campaign. I chose plausible textures for each day based on noted weather events the author mentioned, and guesswork. I use 10 different skies, which gives good variety. There is cirrus, cirrocumulus, cirrostratus (almost smooth overcast) and persistent contrails among them, in varying sky coverage.
It's SO nice to not have the same old upper sky every mission!
I'd be astonished if no one else has stumbled upon this. And for all I know, later versions might permit varying high cloud selection?? At any rate, this is a way for us dinosaurs at least to enoy more variety.