Old Airmail I hope I can show and explain this good enough so you get an idea here of what I am going to show.
All shots here are with REX clouds.
Lets start with the basic FSX loaded up without touching any settings.
Notice the cloud layer itself pretty much compact and defined to roughly 5700 to 6700 ft. AGL.

To view and confirm what we are seeing we go to Free Flight/Current Weather
Select User Defined Weather/Advanced Button.
This is your current Cloud setting for FSX which you seen in Pic 1
Notice the
Cloud Type=Cumulus
Cloud Coverage=Few (2/8)
Tops MSL=6731
Base MSL=5746
Also illustrated in the Blue box to the left of the page.

Now watch what happens when I pull the light blue lines in the blue field up to 10,000, and the bottom part of the line down to 2000 .
Cloud Type= the same (Cumulus)
Cloud Coverage=the same (Few 2/8)

Same Clouds, we just gave more room for them to open up and stretch and breath so to speak.

Have fun and expirement, you will find many ways and settings to set your Clouds and weather up much more to your liking. I love questions.
Thank you for the replies, much appreciated fellas.