Update-I got lucky and drilled a hole that just misses the canvas. I wanted to get as close as possible. I plan to use small stainless washers (perhaps cut on one side and smoothed) with the flat side towards the canvas to give me a larger backing plate. (update-large flat fender washers slide up under the canvas and allow the hole to be right next to the canvas). Alternatively, I may get a thin strip of aluminum or stainless and run it the length of the penthouse along the side of the canvas and drill holes for the bolts (update-this still may be needed at the point where the two tracks meet, the holes are so close together that they prevent using two washers).
I think I will be able to get the track inboard just enough so it will lie flat and not overhang the edge.
Note-the supplied bolts are not long enough to penetrate the bottom of the shell. I had to go get longer. There is a wooden panel near the edge of my penthouse (sandwiched between the fiberglass).
Also, while I am installing a Thule system, I am using the Yakima tracks. I have been told (and verified (?) on the net) that they are the same extrusion.
When lining up the two 5 foot sections of track, I noticed that the holes at the end of each track did not line up. I got out the trusty micrometer and they are almost 4 millimeters offset (2 each?). As I'm writing this it just occurred to me that I should have turned the track around and checked if I would get better alignment...
Anyway, bottom line, the holes are not in the center of the tracks. Poor quality control for a company that sells itself as a high end roof rack manufacturer. Performance should be fine.
Also, I discovered that both of the T moldings holding up my interior ceiling panels had migrated (both to the drivers side). One poked a hole in the canvas.
I removed them and will either leave out (looks fine) or install shorter ones and tack them in place with glue.
For those interested, the construction of the penthouse is fiberglass, some wood sandwiched in), 2 layers of reflectix, and wall panel for the ceiling. That's it.
Any crinkling noises people hear when walking around is the reflectix. I wouldn't worry about it. Popping noises would be fiberglass cracking (unlikely) but I would walk on the areas with wood under them just to be safe.