I've run Yakima A towers, or other gutter mounts, on my 40s, 45 Troopy, 60 and 80 series rigs without issues. Max roof load, distributed over 6 mounts, was about 400-425 lbs., which included a RTT (Hannibal), awning, 2 kayaks (140lbs.) and 10 gallons of fuel. Not ideal, but didn't affect the...