Here is how I did it. The second message in the thread shows pictures. Cheap and effective. While I used 6 brackets per panel, 4 per panel is lots.
Z brackets from most solar providers are VERY expensive for what you get.
http://www.rvforum.net/SMF_forum/index.php/topic,106669.0.html
As others have noted, you will have to screw it down to a wood / rubber roof. I used butyl tape under the mounts as a sealer. Seems to be working well.
Frank.