Frankly, I agree with semidieu. You'd probably be better off faking the atmospherics with some transparent cones or pyramid primitives. It'd speed up your renders considerably.

Every time I load up the file, the spotlight goes back to 100%.

Earlier this week, maclean pointed out a way to stop that. You'll need to open the file in a text editor, find the light's Scale dial, and set the min and max limits to the same value. Then set forceLimits to 4.

http://www.runtimedna.com/mod/forum/messages.php?forum_id=43&ShowMessage=161232