I made a U joint plate and mounted them there. I wonder if length and angle have alot to do with noise and vibration/ clunk noise? Since my bars are two and a half by two and a half square tube 1/4 inch wall i use to take a big cresent wrench and 4lb beater and tighten them up. I havent in a few years.
Mine are 2.5" square 3/16" wall and over 7ft long. They run from the u bolts to the back of the front door. I also snug them up with a BFA and a hammer