This thread is scaring me, since I now have a heavy rooftop box and rack on my top, and I recently cinched out four links. SMB Indiana told me 4 was ok but no more without additional strengthening. Also, it's a bear to lift, but I plan to rarely if ever attempt it with all of that stuff in my box. I usually pull out stove, chairs, and sleeping bags first. Anyway, I wonder if very many people have bent penthouse bars and how exactly?
Sorry for the distraction. Intriguing stuff though.