I need to load several kmz files at one time via Google Maps API, and want to control the opacity for some of the kmz files. Is there a way to do it?

I checked https://stackoverflow.com/questions/4651930/using-a-kmllayer-object-within-the-google-maps-api-is-it-possible-to-allow-a-us, but the methods do not work for me.

By editing opacity via the css, the whole map's opacity will be changed...