My chuck wagon and Rip VanWinkle my 4x7 tiny teardrop both have filon skins. I had previously built Chubby and installed a Lexan roof and took my lead from this my first build. I have had NO leaks and no problems what so ever with any of the 3 builds. I love the Filon.
I had no support for either filon roof other than the spars themselves. They were placed 1 1/2 by 1 1/2 (actual) 2x2's at 12" on center and the voids were filled with 1 1/2" of ridged foam with a filon ceiling underneath in the sleeping area of the 4x7 only.
A few hints.. Drill the holes slightly oversized to allow the material to breath without binding. I would use the decorative rosettes with a bed of 100% clear silicone to disperse the clamping force. They were screwed directly into the spars. Try and find a pleasing patern so many inches in from each side to keep the look consistant. Tighten the screws snug but not tight tight tight.
Most importand do NOT get any of the filon cuttings or dust in your eyes or nose, I got one hell of an eye infection do to my macho attitude about eye protection. I won't make that mistake twice
Here is a build link to the 4x7 build with lots of pics so you can see how thre roof was done.....
http://www.tnttt.com/viewtopic.php?f=50&t=38489The chuck wagon roof is located about page 7 of the tiny barn build in the tiny house thread if you want even more pictures
Good luck in your build.... Bob