I currently have mine set at 12 in the config (previously trying to get more overcast out of other weather engines), but was wondering if anyone has experimented with this in Opus, or if Opus has any recommendation directly. I'm beginning to think that 12 might not be necessary with Opus!

It's not necessary based on my experience...mine is at the default value (8?). Cloud cover is impressive even so.

Thanks, I'm trying it now with a comparison at KIAH, with metar saying clouds broken at 5000. At Cloud Coverage 12 it appears completely overcast, not one spec of blue. At Cloud Coverage 8 clouds are coverage around 65-70 percent of the sky. According to the definition of broken clouds, BROKEN CLOUDS: Clouds which cover between 6/10 and 9/10 of the sky. SO indeed cloud coverage 8 is much more accurate. I might bump it up to 9 or 10 as my personal preference for a bit more clouds, but certainly 12 is overkill.

I have found 10 to be a nice value between clouds and performance

I wouldn't go any higher than 10. I wound up leaving it at 9, and broken clouds covered 90% of the sky, so that was at the heavy end of the spectrum already. I think any more than that would not produce accurate results.

At present broken is set to 6 octars and by definition it is between 5 and 7 octars.

All other cloud is set to maximum, few 2 octars, scattered 4 octars.

Thanks for the answer. One quick question about "Mist"..... Can you explain what it actually is in the sim. I noticed it is disabled as a default. Thanks.....

The mist effect places a thin layer of cloud on the mist layer so that it is visible from above.