Installing solar panels on roof of my Bounder

I am planning to install solar panels on the roof of my Bounder. I call Fleetwood and they said that the plywood is 1/8" thick. I have seen panels installed on other RV's, including Bounders, and it looks as though the installation went well. In fact, most of the folks that I have seen installing the panels (youtube videos) don't seem to even screw into structural members.

For those of you who have installed panels, can you tell me how you secured your panels to the roof? For those who attached only to structural members (like the ribs, etc), how did you locate those members?