Attaching Solar Panel to Roof of 98 Lance

UPDATE: I used 3M Marine 5200 Adhesive with a 5 day cure time. After 4 days it seemed rock solid. I was leaving 6 days after installation and was feeling a little leery with just the adhesive so I put Eternabond over the 22 inch length of each bracket. Seems very solid. I wonder how I might ever remove them if needed.

Thanks for all the input. I'm confident I'll be able to make a secure installation now.

I would advise caution with the whole idea.
Those roofs are often 3/4 x 1" lumber, so drilling 3/8" hole is like taking 30% of the load capacity, what is not too big to start with.
I am carrying canoe on my roof, but I made long support that attach to factory railing.
Other thing is practicality of roof mounted panel.
I camp mostly in Sierra on lots that are 90% in the shade, so roof mounted panel would not work for me at all.
I am carrying single panel and 50' of extension wire for it, so can move it to spot with direct sun and by repositioning it couple times get max charge.

You can also get these Instapark® ZJ-34B Universal Drill-free Solar Panel Rooftop Mount that does not require you to drill holes. From the write-ups I have seen on these once they are mounted to your roof they do not come off. Just copy, and search and you can find them in Black or white.

I put a solar panel on my 2001 Lance. I emailed Lance and they sent a drawing that showed where the framing was underneath the aluminum roof. I made sure I positioned the panel so that at least some of the screws went into the framing. Don't remember what type of screws I used, but it's stayed on for over 90K miles of travel! :)

Look at the "Camper Add-Ons" part of my website and you'll see where the panel is located.

Definetly do not use lag screws, the material on the roof is 1/4" plywood. Do a search on installing solar panels on the net you will get lots of hits. personally I used stainless steel wood screws. One source for info that I can suggest is amsolar.com.