So a few things on mine. When I researched this originally no one seemed to know if you could use the gutters. You would hear people argue both ways. I had a big trail trip coming up in the fall and decided to just try. I don't have a Thule, mine is just a cheap Surco. That said, I think the Thule's will work even better bc of how they latch. On the Surco it's just a bolt clamp with two terrible pieces of rubber that kept coming off. I ended up taking the feet off and rubber dipping them. Took a few coats but it appears to be holding up. As for the weight, I put all my camping gear up there and the Jerry can with no issue. I now have the ARB duel can holder and feel pretty confident it'll hold even on the trail.
I think the biggest reason most don't use the gutters is bc if you do obviously you can't take off your freedom panels. For me this isn't a big deal bc I only have this set up in the fall and winter. Soft top goes on in the spring and I just have to pack lighter for a camping trip. Hope this helps! I'm far from an authority and we surely don't have the trails here in VA like you guys out west but I can tell you what has worked for me.
