Howdy,
Just a quick up-date... I ran a few activities today in Open Rails with the MSTS Environment checked and all looked as it should with no gaps between the cloud layer and horizon, which seems to tell me that Open Rails does read the parameters in the Environ files correctly. I have to admit, I was highly impressed with the positives of having MSTS Environment checked as compared to 7-8 years ago when it looked like crap. Another test I did was to run with MSTS Env unchecked and the weather randomization set to zero and it produced the gap again. This gap issue is not new and has been around for quite a while. I hope the OR development team digs into their coding for a solution.
Peter